Author:Anahi – Page 2 – Maryland Grows

Support Our Insects at Night

June 12, 2024June 11, 2024Maryland GrowsLeave a comment

We tend to think about protecting our insects when and where we see them. This is perhaps why we may have a higher propensity to think about protecting pollinators we can see flying around rather than organisms that live in the darkness of the soil or hidden in the leaf litter. In today’s post, I would like to bring some attention to other groups of insects we may tend to forget about but which we can also help protect: insects that are active at night.

Don’t insects sleep at night?

Although many insects are generally less active at night due to the lower temperatures and their inability to move when the temperatures drop below a certain threshold, many insects are adapted to being active at night. For example, if they are pollinators of nocturnal or dusk-flowering plants such as several moth species are, they will be active when darkness falls. Other insects are active at night as predators, or at certain times of the season looking for mates and egg-laying sites. For all these insects, the absence or reduced presence of light is important for allowing them to take on what they need to do to survive and/or reproduce. For this reason, the presence of artificial night lighting in our outdoor spaces, especially in the warmer periods of the season, can interfere with these insects, leading to potentially very negative effects.

How can outdoor night lighting affect nocturnal insects?

Insects can be perturbed in different ways through outdoor night lighting. One of them is its potential interference with their temporal rhythms. In fact, like most animals, insects use light-darkness and the presence of certain night sky cues (e.g., full moon) to regulate their developmental cycles and perceive the progression of the season. The presence of supplementary lights during the night hours can lead to altered developmental cycles, making them longer or mismatching those of organisms belonging to the same species. This can lead to the insects missing their optimal mating times, losing their ability to forage on specific plants, or properly preparing for the arrival of colder nights as the season progresses.

a string of lights is hanging over a a garden firepit area at night — The use of often non-essential lighting, such as light strings and other nocturnal accent lights in our spaces, can negatively affect the development, survival, and reproduction of many nocturnal insects. Photo: P. Danilyuk (CC)

Another issue that artificial nocturnal light can produce relates to the spatial disorientation of nocturnal insects. This can occur when insects are attracted to nocturnal light sources instead of moving towards their optimal habitat. This can lead to increased predation in those areas (the insects become more exposed to being seen), as well as their spending valuable energy by spending time in an inhospitable region. Further, disorientation can happen in a more indirect way by the light’s interference with the patterns present in the canopy. In fact, many insects have been shown to use the contrast pattern of the canopy and the sky to navigate and identify optimal habitats. The presence of nocturnal artificial lights can lead to the disappearance or a stark modification of that contrasting pattern, interfering with their ability to find their way in the ecosystem and decreasing their ability to find a proper habitat for their survival.

two fireflies light up at night — Some insects like fireflies use bioluminescence for inter-species recognition and mating. Photo: T. Ota (CC)

In some cases, the presence of nocturnal artificial light can interfere with mating and intraspecific recognition behaviors. Many groups of insects, such as fireflies and glow worms, use light cues to attract and recognize each other. In regions such as ours, where fireflies represent such an important part of our ecosystem, the use of outdoor nocturnal artificial lighting can interfere with the finding of mates and can potentially lead to much reduced abilities to reproduce and sustain populations.

What can we do to reduce this type of nocturnal pollution?

The obvious answer to this question is that if we want to reduce this type of pollution, our best bet is to turn off non-essential outdoor night lights, in particular during times of the year when insects are active. Doing this may actually save us some money, but also will allow us to support a higher diversity in our area, all while potentially letting us appreciate even more the nocturnal activity that may be present in our region. For example, doing this may make it easier to support fireflies and participate in their conservation, but can also support the reproduction of plant species that depend on nocturnal pollinators.

If leaving lights on is unavoidable, one should consider the intensity that is being used. Can the light be dimmed to a lower intensity? Could it be filtered to display a color that is less disruptive to insects? The Xerces Society has put together a really neat guide on this (Firefly-Friendly Lighting Practices – PDF), and I strongly encourage you to consult it if interested.

Finally, another way we can contribute to reducing unnecessary night lighting is by engaging in our communities. Initiatives such as DarkSky can help with this, both promoting best practices at the community level and engaging in conservation through community certification programs that are conservation-effective. You can learn more about these nocturnal conservation programs here.

By Anahí Espíndola, Associate Professor, Department of Entomology, University of Maryland, College Park. See more posts by Anahí.

Anahí also writes an Extension Blog in Spanish! Check it out here, extensionesp.umd.edu, and please share and spread the word to your Spanish-speaking friends and colleagues in Maryland. ¡Bienvenidos a Extensión en Español!

The Shared History of Wasps and Bees, And How Bees May Have Become Vegetarian

May 13, 2024May 10, 2024Maryland Grows3 Comments

We may have all found ourselves in that situation in which we see an insect on a flower and we wonder whether it is a wasp or a bee, and we may have also seen people panic when they encounter a bee, thinking that it is indeed a wasp. Although the two groups are very distinct and there are several ways of telling them apart (check out this previous post to see how to do it), this difficulty is in part a signature of the shared evolutionary history that the two groups have. In today’s post, I want to tell you about the evolutionary origin of bees, how it is interwoven with that of wasps, and how evolutionary studies can help us understand and explain the diversity of our charismatic bees.

Evolutionary histories and the big family we are all part of

Before jumping into the main topic of this blog, please bear with me so I can give you a bit of context for what I’ll tell you, and so you can fully appreciate the power of the discoveries I will tell you about in just a second. One of the foundations of today’s biology and the way we understand life is that living organisms share a common ancestry and that evolutionary processes such as natural selection, mutations, dispersal, and random processes have led to the establishment of new lineages that can evolve into new species and new groups of organisms. What this means is that all the living organisms we know can be placed in a sort of genealogical tree, where more closely related species and groups appear placed on branches of the trees that are also closer to each other (we call these trees “phylogenies” or “phylogenetic trees”). Also, this means that if we were to take these trees, and we were to follow the evolutionary process “backward” (from the tips to the internal branches; that is, from the present into the past), we would be able to identify branching points, which represent the now extinct ancestors of species we know today.

a diagram of a family tree — A phylogeny can be compared to a genealogical tree we may want to build for our family. In this tree, the most closely related members of our family share recent ancestors (marked with diamonds), but are still connected with more distantly related members of the family with longer branches and other more ancient shared ancestors. In the same way, a phylogeny represents the relationships between species or groups of species, with branches connected by their shared ancestors. Image: University of Iowa

Although this may sound like a biological nerd moment of mine, I hope that you will appreciate the enormity of this principle. This simple concept indicates that each of us and all species that exist on the planet have shared ancestors at some point in our history. We are all related to each other, like a huge family… and as for all families, the study of our history can teach us fun and interesting things about who we are, helping us understand and explain things we observe today. Let me tell you what the study of these phylogenies has taught us about wasps and bees (and their shared history) and why this excuses us in part from not always being able to tell them apart 😉.

Bees and wasps, and the vegetarian wasp

As you may know, bees and wasps are both insects that belong to the order Hymenoptera. Despite the fact that people knew they were related but distinct from each other, it was not until relatively recently that people understood what that relationship was. In fact, because they share a lot of common traits, scientists were for a long time confused about what the most closely related group of Hymenoptera was for bees, wasps, and ants. Some years ago, with the development of new methods that allow for more detailed studies of phylogenies, researchers found strong evidence that ants are a group of organisms that is related but distinct from another group formed by bees and by a particular group of solitary and usually ground-nesting wasps called crabronids. Besides the taxonomic and purely conceptual importance of this discovery, what this meant biologically was on the one hand, that bees are evolutionarily extremely closely related to wasps, to the point that we could consider them “non-carnivorous wasps”. On the other hand, this discovery showed that all bees we know today would have evolved from a wasp-like ancestor that was solitary and ground-nesting, like the crabronids we know today.

a family tree of bees and wasps - showing evolutionary relationships — In 2017, Branstetter and collaborators used phylogenies to demonstrate that all bees and a group of wasps (crabronids) shared a common ancestry, indicating that bees can be considered a type of “vegetarian” wasp. In the figure, the position of the common ancestors is shown with arrows and stars. The main groups are labeled on the left. Image: modified from Branstetter et al., 2017

If you’re like me and find this fun, keep reading because it gets even more fun! 😊 So, after this discovery, the people who work on these topics wanted to know more. For example, can phylogenies tell us more about how the transition from a meat-based diet (wasps are carnivores) to a pollen-based one (bees feed mostly on pollen and nectar) could have happened? To investigate this, researchers ran a similar analysis, but this time considering a lot more species of both bees and crabronids. Constructing phylogenies using genetic information, they figured that when the evolutionary relationships of these groups were studied, it appeared that bees were the most closely related to a particular group of crabronids that is known to predate on thrips (a family called Ammoplanidae).

a closeup of a small black bee — Bees have been shown to be very closely related to a group of tiny wasps in the family Ammoplanidae which are known to hunt on thrips. Photo: CBG Photography Group (CC).

Besides confirming the discoveries of the previous study, this one provided a logical and interesting biological and ecological context for the transition from carnivory to pollinivory in bees. Thrips are a group of insects known to feed on plant materials, often found on flowers, where they feed on pollen. This new study proposed that a possible evolutionary opportunity may have appeared when a lineage of thrip-predating wasps evolved the ability to not only digest thrips meat but also the pollen they contained in their guts (!!). This transition could have set the evolutionary foundations to eventually transition to a diet fully based on pollen, which opened opportunities to the newly emerging lineage to feed on a new dietary resource not already in use by other wasps. If this is true, this transition would have provided an important evolutionary advantage (e.g., reduced competition for food), which would have led to the huge diversification of bees, leading to the extreme diversity we see today.

By Anahí Espíndola, Assistant Professor, Department of Entomology, University of Maryland, College Park. See more posts by Anahí.

Anahí also writes an Extension Blog in Spanish! Check it out here, extensionesp.umd.edu, and please share and spread the word to your Spanish-speaking friends and colleagues in Maryland. ¡Bienvenidos a Extensión en Español!

Research Update from the Serpentine Grasslands: Pollinators in a Rare and Endangered Habitat

April 8, 2024April 4, 2024Maryland GrowsLeave a comment

Did you know that before European colonization and thanks to native land management, the area that is now northern Maryland was home to thousands of acres of sprawling prairie-like grasslands? It’s a pretty cool thing to imagine, right? Instead of dense urban centers, highways, farms, and patches of forest, most of Baltimore County would’ve been a nearly treeless ocean of swaying grasses and wildflowers! Instead of cars, shopping carts, and the hustle and bustle of people, you’d see majestic herds of deer and elk, a horizon dotted with flocks of birds, and the busyness of bees and butterflies. You can read more in a previous blog post about these eastern ‘Serpentine Grasslands’. Sadly, these grasslands no longer exist in the formerly massive extent they used to occupy, but several preserved remnants still endure here in Maryland to tell the tale of their former glory!

a view of the Maryland Serpentine Grasslands on a cloudy day — *A stormy summer evening at Soldiers Delight Natural Environment Area, Baltimore Co. – one of Maryland’s Serpentine preservation areas. Photo: Justin O’Neill*

What is the current status of the Maryland Serpentine Grasslands?

Many historic and contemporary human-driven environmental changes have caused these special ecosystems to dwindle to the point of concern; it is currently estimated that only 1.6% of their historic area in the region remains. This precipitous decline of eastern Serpentine Grasslands is concerning because they support many special plant species that are considered threatened or rare in Maryland. Luckily, several private and governmental organizations have taken to conserving and studying these ecosystems in Maryland and elsewhere (check out some of them here: Soldiers Delight and Lake Roland). Although eastern Serpentine grasslands have attracted considerable scientific research interest in terms of their rare and unique plant life, the animals that call these critically imperiled habitats home are virtually undocumented (with the exception of some rare butterflies and moths). Could there be special Serpentine associated species that we have yet to even notice?

a purple wildflower found in the Maryland Serpenine Grasslands — Phemeranthus teretifolius, the Quill Fameflower, is one of the special plants that makes its home on the dry and rocky soils of Serpentine habitats. The flower is only open during a few short hours in the afternoon, during which it is abuzz with small solitary bees. Photo: Justin O’Neill

The mission of knowing what lives there to better protect it

To address this knowledge gap, our team at the EspíndoLab, have set out to start documenting the insects present in Maryland’s Serpentine Grasslands. Our current focus is on flower-visiting insects that could act as pollinators, specifically bees and hoverflies. Given the many rare and threatened plants documented in these areas, we figured it was important to first know what insects might be helping most with Serpentine plant reproduction.

How do we do this?

To document these flower-visiting insects, the lab crew has undertaken 5 years (2019 – 2023) of observations and insect collection in three of Maryland’s most intact Serpentine Grassland conservation areas. Because different flowers bloom during different parts of the growing season (spring to fall), we had to visit these conservation areas many times each year to observe the full range of flowering plants and their insect visitors. So, once every two to three weeks across each season, the Serpentine squad would head out to visit our many field study sites and systematically capture bees and hoverflies seen interacting with flowers. Currently, we are working on the meticulous process of examining each captured specimen with a microscope to determine its species identity using taxonomic guides.

a student researcher collecting insects at the Maryland Serpentine Grasslands — Nets at the ready! The Serpentine squad carefully captures bees and hoverflies seen visiting flowers at several study sites across three of Maryland’s Serpentine conservation areas. Photo: Justin O’Neill

With this information we can begin to catalog the insect species that make up Serpentine pollination communities. This allows us to explore if the communities present in the Serpentines are different from those in nearby habitats and if they possess any rare or unique species. This information will also give us insight on how the plant and pollinator communities interact with one another; informing us about key species that contribute vitally to pollinator persistence or plant reproduction. Ultimately, the knowledge we gain will provide a baseline understanding about the dynamics of pollinator diversity in the grasslands and inform the organizations that conserve and restore these ecosystems.

What are we learning?

So far, the EspíndoLab’s efforts in the grasslands have revealed quite a bit about the broad array of insects that visit these unique plant communities. Notably, among the myriad of beetles, butterflies, flies, and wasps that visit Serpentine flowers, native solitary bees and hoverflies are consistently observed to be the most abundant – and perhaps most important potential pollinators. Interestingly, social bee species, particularly honey bees, that are commonly observed in many pollination communities, were infrequently encountered in our collecting efforts until late in the season, if it all. This suggests that they may pass on the relatively sparse floral resources of the grasslands until the Fall, when dense and attractive patches of goldenrod and aster bloom – potentially providing them an important source of resources as pickings become slim late in the season.

Most excitingly, our collections have revealed 39 unique genera of bees and hoverflies in the grasslands, so far – with more likely to be found as we continue to identify the many insects from our collections. Our efforts have also found several rare bee and hoverfly species; some of which are insects that have never been observed in Baltimore County! Among these rare and interesting finds are two bees and a hoverfly that are particularly special.

The hoverfly, Trichopsomyia litoralis, is relatively new to science – having only been described in 2019. Not much is known about the ecology of this species, but its larvae are known to feed on economically important pests. Encountering this species in the Serpentine grasslands is interesting not only because it is rarely observed, but also because it is currently thought to only inhabit an eastern coastal range (likely associated with sandy sites)! This information could extend our understanding of this hoverfly’s distribution or suggest that these flies undertake long migrations during their life cycle.

On the other hand, we have found two rare bee species that are really cool: the mining bee, Andrena gardineri; and the nomad bee Nomada seneciophila. These bees are what we call specialists: they have very specific ecological requirements. For example, A. gardineri is known to preferentially forage for pollen on plants from the genus Packera (ragworts or groundsels) – it is considered a Packera specialist. Even though A. gardineri is quite rare in the region, we find it commonly during our spring grassland collections. This is because almost all the conserved grassland areas provide good conditions to host lots of Packera anonyma.

close-up of the face of a bee found in the Maryland Serpentine Grasslands — *A close-up shot of a fluffy male Andrena gardineri specimen. Photo: USGS Bee Monitoring Lab / Brooke Alexander.* *CC 2.0*

The other notable bee we observed, the nomad bee, Nomada seneciophila is a vanishingly rare cuckoo bee (see here what these bees do and why this is fascinating). These bees wander (nomadically so) around in search of other bee’s nests so they can hijack them for their own young to develop in! N. seneciophila, as it turns out, is a specialist of our specialist friend, A. gardineri. That is, this nomad bee species has a very strong preference for stealing the nests of our other rare bee, A. gardineri!

another bee found in the Maryland Serpentine Grasslands — *The waspy-looking Nomad bee: Nomada seneciophila. Photo: Justin O’Neill*

From these interesting encounters, it is becoming increasingly clear that these grasslands not only support remarkable plants; they also provide critical resources and nesting habitat for rare bee and hoverfly species. Although these once expansive ecosystems might not exist on the grand scale they once did, their remnants are unique contributors to the region’s biodiversity. Taking the time to document their floristic and faunistic wonders is important for understanding the historic role they played in shaping regional biodiversity today, and how that biodiversity may respond to the changing environments of the future!

By Justin O’Neill, Ph.D. student, and Dr. Anahí Espíndola, Assistant Professor, EspíndoLab, Department of Entomology, University of Maryland, College Park.

Stem-Nesting Bees in Maryland

March 11, 2024March 8, 2024Maryland Grows1 Comment

With their large diversity, bees display a huge variety of nesting preferences. Some bees that are relatively commonly encountered in our region are those that nest in stems. In today’s post, I want to tell you about who they are, their biology, and their preferences when the time comes for them to pick their nesting sites.

Who are the stem-nesting bees in our region?

When we consider bees that nest in stems, we can think about two main groups. In the first group, we have bees that actively dig into pithy stems or wood to build their galleries. In the second group, we have those that use pre-existing cavities in stems and slightly adjust them to accommodate their brood. This difference may seem trivial; at the end of the day, they will all end up in stems, right? Well, that is true to some extent; however, whether we talk about one group or the other will define what actual taxonomic group of bees we’ll be referring to, and a different set of morphological adaptations that allow them to build their nests properly.

In our region both types of bees are present and many of them are relatively common and easily observed in our green spaces.

Stem nesters that dig their nests

In addition to large carpenter bees (Xylocopa), this group includes Halictid bees such as Augochlora and the Apidae Ceratina. Because they all have to dig actively into stems to build their nests inside, all these bees are equipped with very strong mandibles, which have modifications that reinforce them, and strong muscles that allow them to increase the force they can exert on the stems.

a metallic green bee going into a stem nest cavity — Metallic bees are very common in our region. They often can be found emerging or looking for wooden resources to build their nests. Photo: K. Shultz (CC).

Depending on the species, we can find them building nests on different substrates. While Augochlora can often be found building galleries in rotten logs, Ceratina is mostly associated with stems that tend to be a bit hollower, such as those of raspberries and blackberries (you can check out this other post on how to trim those plants to protect their nests), or those of plants of the genus Verbena. In all these cases, the nests have the shape of a gallery, with small cells built consecutively. Each of these cells is carefully built, provisioned with nectar and pollen, populated with one egg, and finally sealed with sawdust or compacted pith.

Stem nesters that use stem cavities that already exist

Several families of bees belong to this group in the Mid-Atlantic. Species of the genus Hylaeus in the family Colletidae are present in our region, and readily nest in hollow stems. Another group that is very commonly seen in our region is that of leaf-cutter bees (Megachilidae). Although this group tends to be more flexible in the types of cavities they will use for building their nests, many species will readily use natural or artificial “stem-like” cavities (these bees are very common in bee hotels).

several bees nesting inside of a plant stem — A small bee commonly seen in bee hotels is that of genus *Hylaeus*, also known as the yellow-faced bees. These bees will readily use small hollow stems and cavities. Photo: R. Cruickshank (CC).

Stem-nesting bees (Hylaeus) were observed in a raspberry cane on May 10, 2023, in Montgomery County, MD. Video: Christa Carignan, University of Maryland Extension

Because these groups do not need to actively dig into wood to build their nests, their mandibles are not as developed as those of the other group of bees I presented above. A common characteristic of all these bees is that they have relatively long and slender bodies, which is believed to allow them to move with more ease in relatively small cavities. It is also for this reason that specialists think that all these species transport pollen either internally or on the lower part of their abdomens (instead of on their legs, for example); this reduces their “width” and allows them to fit into cavities that may otherwise be too narrow. Another characteristic of this group of bees is that they often line their brood cells with special materials, such as leaves, petals, resins, or mud. This means that building these nests is a lot of work!

leaf-cutter bee carrying a leaf piece to a nest — Leaf-cutter bees of genus *Megachile* are also very commonly seen in bee hotels and nesting in cavities around our homes. Here, *M. centuncularis*, brings leaf cuttings to line the nest in a cavity offered in a bee hotel. Photo: B. Plank (CC).

Although bees (and most insects) are generally negatively affected by urbanization, this group of bees appears to benefit from their interactions with humans. Unlike ground-nesting bees which are very negatively affected by land development and urbanization, it seems that stem-nesting bees can easily use many cavities created by humans, such as those appearing in buildings, walls, fences, and gardens.

Read more: This Year, Host Bees in Your Garden

By Anahí Espíndola, Assistant Professor, Department of Entomology, University of Maryland, College Park. See more posts by Anahí.

Anahí also writes an award-winning Extension Blog in Spanish! Check it out here, extensionesp.umd.edu, and please share and spread the word to your Spanish-speaking friends and colleagues in Maryland. ¡Bienvenidos a Extensión en Español!

Help us improve the Maryland Grows Blog! Please complete our brief survey to give us your feedback and let us know about your interests.

A Little-Known Group of Pollinators: Beetles!

February 12, 2024February 12, 2024Maryland GrowsLeave a comment

As we mentioned in previous posts, when we think about pollinators, we tend to think of butterflies and bees, but rarely about the super important hoverflies or other groups of organisms. In today’s post, I want to tell you about another of those little-known pollinator groups; let’s talk about beetles that act as pollinators!

Beetles: “hard-shelled” pollinators

From a taxonomic perspective, beetles are a group of insects that belong to the Order Coleoptera. Among other important characteristics, they are recognized by their extremely well-protected body, in particular by structures called “elytra”, which provide a very hard cover to their wings (the wings are placed under the elytra). Generally, beetles have mouth parts that are adapted to chewing, which means that they have large mandibles that allow them to break their food. You may be wondering why I am talking about these structures in a pollination post… well, as for all pollinators, the shape and function of a pollinator define what they do (and don’t do). Let’s see how this affects our pollinating beetles.

a black and yellow beetle on a purple flower — Beetles are common flower visitors, with some of them being very effective pollinators. Because of their very well-protected bodies (see elytra covering the “back” of this beetle), they often spend a lot of time on flowers, where they feed on pollen, nectar, and floral parts. In this picture, we can see a cetoin scarab beetle with prominent elytra and a very hairy body that helps them transport pollen grains between flowers. Photo: C. J. Sharp (CC).

In the case of beetles, the fact that they are well protected by those elytra makes them more “confident.” That “hard shell” provides a great deal of protection against predation by other arthropods, which in turn makes them generally more “chill” in their visits to flowers. Unlike butterflies, bees, or hoverflies, beetles tend to move little within and between flowers, taking all their time to get the resources they need from them. For this reason, they are often considered as more generalist and inconsistent pollinators than their less-protected counterparts.

The shape of their mouths and their feeding habits also affect their efficiency as pollinators. In fact, beetle visits to flowers tend to be relatively destructive because they are attracted to them by their floral tissues, including in some cases pollen and the ovaries! In this respect, beetles tend to visit flowers to feed on them, which in some cases can lead to floral destruction. So, given this, are beetles good pollinators or just flower herbivores?

Beetles as pollinators

Among all the many different groups of beetles, some of them are considered to be particularly good pollinators. Specifically, these belong to the beetle families known as soldier (family Cantharidae) and longhorn (family Cerambycidae) beetles, families that depend on floral resources for their survival at least at one stage of their development. Other families such as scarabs can also be strongly associated with flowers for their survival. In all these groups, the beetles in question have clear adaptations that make them good agents of pollen transfer. For example, we observe different parts of their bodies covered with abundant hairs. This improves pollen transport and thus increases their ability to effectively cross-pollinate the flowers they visit.

a beetle with pollen grains on its head — Beetles that are good at transporting pollen have hairier bodies that can carry pollen grains, like this cantharid beetle that got its face covered in pollen while visiting these flowers. Note the yellow “powder” – pollen – that covers part of the beetle body and take a look at the large mandibles the beetle uses to feed on floral parts. Photo: J. Tann (CC).

Further, although these beetles tend to still feed on floral parts, they are usually much less destructive than their more generalist cousins. They often feed on specific flower parts (instead of on all the floral sections), leaving the central reproductive structures (e.g., the ovaries) intact, and thus allowing plant reproduction. These beetles are also often more specialized in their floral choices, preferring a small range of plant groups (usually one or a few species within the same plant genus), and moving more readily between flowers. Combined, all of this means these beetles can not only carry a lot of pollen (they are hairy) but also move it from flower to flower more effectively and do not destroy completely the flowers they visit.

A cool beetle pollination example

Beetle pollination is a very understudied topic in temperate regions such as Maryland, and we are still learning a lot about it. It is thus not surprising that the number of examples from our region is not super high. Let’s talk about one of them that happens to be relatively well-studied elsewhere but that also occurs in North America.

yellow and black soldier beetle on a magnolia flower — Beetles are considered some of the most important pollinators of species of the genus *Magnolia.* Here, a long-horned (Cerambycid) beetle on a *Magnolia grandiflora* flower. Photo: D. Hill (CC).

An example of beetle pollination of native plants that are also present in our region is that of Magnolia flowers. Although most of our knowledge on the pollination of this plant genus comes from studies done on species outside of North America, there are a couple of reports of floral visitors in several of our local species. From elsewhere, we know that these trees display flowers that appear to be particularly attractive to beetles: they are white, easily accessible, offer a lot of pollen, are fragrant, and in some cases even produce heat! In many of these species, the flowers appear to attract scarab beetles, which, once landed on the flowers, feed on the petals, mate, and then actively move between flowers and cross-pollinate. In North America, some studies like this one and this other one (in PDF) have found a wide variety of beetles attracted to our native species. Many of these beetles are very small and visit Magnolia flowers to feed on them, mate, and spend the night protected within the flowers.

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How Do We Study Pollination?

December 11, 2023December 11, 2023Maryland GrowsLeave a comment

Pollination is such a buzzword right now, and a lot is said about pollination and pollinators. However, how do people learn about pollination and pollinators? How do people know who the pollinators are and how pollination works? Because I happen to do research on pollination, I wanted to use this opportunity to share with you some insights into how pollination is studied, what it teaches us about plants and their reproduction, and how this connects with the things we hear about pollination.

What are we studying when we study pollination?

As we mentioned in previous posts, pollination is basically how plants reproduce. Generally, pollination involves the deposition of pollen grains on the female organs of a plant, which in many cases leads to ovule fertilization and often the production of seeds and sometimes fruits. So, when we study pollination, what we are studying is the reproductive strategies of plants. If we think about plants and the many different ways they have to reproduce, it may be simple to imagine all the different aspects one can try to understand about pollination. Here I will present a couple.

The reproductive strategy of plants – selfing, crossing, or both?

Unlike us humans, many plants can self-pollinate. This means that the species that can do this can technically accept pollen from their own flower and use it to fertilize their own ovules. The consequence of this is that plants that can self-pollinate do not necessarily need pollen from another individual to produce offspring. This may seem like a nerdy technicality of mine, but the ability or not of a plant to self can have a lot of wide-ranging consequences. From an evolutionary perspective, this can affect the genetic diversity in a species or group of species, which can define whether a species can adapt or not to certain conditions, among other things. This can also have consequences for food production and plant breeding; if a plant cannot self, several stocks need to be present in a field for it to be able to produce fruit. This for example happens to some varieties of cherries, where more than one tree needs to be planted in an orchard for the plants to produce fruit.

reproductive parts of flowers — To test for plant reproductive strategies, researchers can perform controlled crossing experiments, which follow generally what is presented in this figure. Image: University of Waikato.

To understand whether a plant species can self, a basic experiment can be done. In this experiment, one creates groups of plants of the same species that will be pollinated following different methods. By comparing the number of seeds produced by each method, one can infer how the plant reproduces. In its simplest forms, one of these experimental groups of plants is manually selfed, which usually involves removing all anthers from a flower and then manually depositing pollen from the same plant on its stigma. In another group, plants are crossed using pollen from another plant. The flowers and potentially fruits of both groups of plants are then left to develop, and once fruit/seed maturity is reached, one counts the number of fruits and seeds per group of plants. If the two groups present significantly different numbers of fruits or seeds, then we can infer whether the plant is able or not to self.

Who pollinates a plant?

Imagine that we figured that a plant requires cross-pollination. Now, a question we may want to ask is how the pollen of one flower can get to the stigma of another flower. Again, this is not just a biologist niche question; this has practical and evolutionary consequences. For example, if a plant is wind or water-pollinated, it will be able to produce offspring in the absence of animal pollinators. Alternatively, if a plant needs animal pollinators, then their absence can lead to the plant’s inability to sustain its population over time. In a food production world, plants that need animal pollinators will benefit from the presence of those pollinators, leading to higher fruit or crop production when more pollinators are present (this is the case of, for example, almonds and strawberries).

To study this, scientists have a large palette of methods. Here are some. One of them involves observation of the flowers in question. For example, one can assume that a flower that produces nectar or that has special color markings aimed at directing pollinators when they visit a flower will be more likely pollinated by animal pollinators than one that does not offer any floral rewards in exchange for flower visitation. Similarly, the general floral shape gives clues about how it may be pollinated. Flowers pollinated by animals tend to have specific shapes that improve pollen deposition by animal visits, while those pollinated by abiotic factors are usually droopy or displayed in very humid areas.

markings on flowers only visible with UV light — Flowers that can look “plain” to us may have special colorations that only pollinators can see, like this black-eyed Susan, which shows its floral markings that can be seen only under UV light (a wavelength many insects can see). Observing markings or “signs” on flowers indicates that the plant may use animals for pollen dispersal and transfer. Photo: A. Davidhazy.

As said before, observations are a huge part of studying pollination and the identity of pollinators of a plant. This generally also entails spending hours upon hours over several seasons carefully observing and sometimes capturing any floral visitor and potential pollinator of a plant population. This requires patience and focus, and careful recording of the abundance, frequency, and identity of any flower visitor. This also often requires hours of identification of captured floral visitors, often under the microscope (given that most floral visitors are often insects), and through the use of taxonomic keys or the consultation of experts of specific taxonomic groups.

a man in a field using an insect sweep net — One way to understand what pollinates a plant involves hours of focused observation of flowers and capture of the animals seen visiting them. Photo: A. Espíndola.

fluroescent dyes are used to track movement of pollen by pollinators — Fluorescent dyes can be used to track the movement of pollinators and the potential for pollen transfer. Photo: Huais et al., 2022.

Along with these hours of observing and describing what is being seen, other more “manipulative” approaches exist. For example, many scientists try to understand who visits a flower by marking flowers with powdery dyes and then seeing if any animal seen visiting the flowers becomes colored with the dyes. More “technological” approaches use high-resolution cameras and artificial intelligence (AI) methods, as well as DNA sequencing to identify the presence and species identity of pollen grains on animals seen or suspected of visiting flowers.

Make Your Garden Shine Like Gold This Spring With Golden Ragwort

November 13, 2023Maryland Grows1 Comment

The golden leaves of the trees outside my window remind me that the growing season is almost over and that winter is coming. However, those same gold colors also remind me that spring is not that far away and at my place, it will start with some gold showing up in my garden. This golden treasure connects the gold of the fall with the gold of spring to close the season’s circle. Let me tell you about what I think is an underrated plant from right here: the golden ragwort!

Golden ragwort – a treasure for our gardens

The golden ragwort (Packera aurea) is a perennial native plant of our region that belongs to the sunflower family, Asteraceae. The species is found pretty much across the whole state and is commonly found in eastern North America. Its name comes from the abundant yellow flowers it produces early in the season (all that gold!), at a time when most other spring plants have not flowered. In fact, in our region, the golden ragwort starts flowering as early as March and continues doing so for several weeks/months afterward.

A species in the Asteraceae family, the golden ragworts displays many inflorescences that are of strong yellow. Photo: B. Gratwicke (CC).

Besides it being a great addition to any space that needs some floral resources, another benefit of this species is its tolerance of a wide variety of growing conditions. Golden ragworts can be grown in conditions ranging from full sun to shade, tolerate heat well, and require some soil moisture. Once established, the plants are great ground covers since they can spread easily thanks to their rhizomes.

After flowering, the rosettes and rhizomes continue to cover and occupy the ground, making them also a great resource to retain water and soil in spaces that may be prone to soil erosion. Related to this, another benefit of this strong ground cover is that because they are so good at establishing, this species can have a high potential for competing against invasive plants that we may want to prevent from arriving or to remove from our green spaces.

Golden ragworts are great ground covers, forming mats that flower for several weeks. Photo: D. McGrady (CC).

And if your green space is like mine, and often visited by deer, this is a plant for you! In fact, because plants cannot escape predation like animals, they have evolved other ways of protecting themselves against herbivores. It turns out that all plants produce chemical compounds that act as chemical shields against herbivory. These compounds can make them toxic or unpalatable to many animals, thus leading to at least an unpleasant and at worst a deadly experience if ingested. Well, it turns out that Packera aurea has some of these defenses! This means that it may not be a great idea to try to eat this plant yourself (in case you were thinking of it 😊), and second, that other mammals such as deer will not feed on it due to its toxicity… making it deer resistant!

What do pollinators think of this plant?

Because they flower so early in the season, golden ragworts are very valuable for pollinators. In fact, because there are often not too many floral resources available in the early spring, early-flowering plants such as this one play a key role in supporting early-emerging pollinators.

Packera aurea flowers have been shown to support a large diversity of bees and hoverflies, and of course, this diversity increases with the progression of the season. Among some of the species it supports are several sweat bees, little carpenter bees of the genus Ceratina, and many species of hoverflies. Interestingly, this species has also been described as one of the preferred pollen sources of the rare pollen specialist mining bee Andrena gardineri.

At the end of the flowering time, the plants create a nice ground cover with their rosettes. Photo: M. Heberling (CC).

When is the best time to plant golden ragwort?

Although the ideal time to plant it is in the early spring, depending on where you are in the state, you may be able to have just enough time to establish it this fall. Either way, the plant gets established very quickly, so if you are afraid of it being too late right now to try it, keep it in mind for the spring and check out your local native plant nursery to get your starts in time! I promise you will not regret it, and you will be thankful every spring for the lovely botanical chest of gold that will enrich your garden.