Ecomorphological Associations of Scapulocoracoid Form in Greater Antillean Anolis lizards

Find the scapulocoracoid

New literature alert!

In Annals of Anatomy
Tinius, Russell, Jamniczky, and Anderson

Summary

External morphological metrics have featured prominently in comparative studies examining the morphological convergence that characterizes anoline ecomorphs. To what degree the appendicular-skeletal morphology of Greater Antillean island Anolis lizards tracks their diversity and ecological adaptation, however, remains relatively unexplored. Here we employ computed tomographic scanning techniques to visualise in situ the scapulocoracoid of ecomorph representatives (trunk-ground, trunk-crown, crown-giant, twig) from three islands (Jamaica, Hispaniola, and Puerto Rico), and compare its three-dimensional geometry using qualitative-descriptive and quantitative-morphometric techniques. In contrast to our previous, similarly-conducted study of the pelvic girdle of these same species, the form of the scapulocoracoid varies markedly both within and between species, with much of the variation relating to phylogenetic relationship, specimen size, and assigned ecomorph category. Morphometric variation that correlates with size and/or phylogenetic signal varies between species and cannot be eliminated from the data set without markedly reducing its overall variability. The discovered patterns of skeletal variation are consistent with the demands of locomotor mechanics imposed by the structural configuration of the microhabitat of these ecomorphs. Most pertinently the ecomorphs differ in the anteroposterior length of the coracoid, the dorsoventral height of the scapulocoracoid, the dorsoventral height of the scapula in relation to the height of the suprascapula, and the relative positioning of the borders of the scapulocoracoid fenestra. In the examined ecomorph categories these skeletal differences likely relate to microhabitat usage by permitting different degrees of tilting and displacement of the scapulocoracoid in the parasagittal plane and influencing the sizes of muscle origins and the vectors of their actions. These differences relate to the amount of humeral adduction applied during its protraction, and to the structural stability of the shoulder girdle during acrobatic maneuvers, thus influencing the perch diameter that can be effectively negotiated, a critical factor in the microhabitat structure of Anolis ecomorphs.

Read the full paper here!

Sneaking into SoCal: the Brown Anole’s Rapid invasion of Orange County, USA

By Lelani Del Pinto & Samuel Fisher 

Southern California has remained relatively unaffected by invasive reptiles for the past few decades. While there have been few invasive species noted, Californians use of citizen science tools has made it easier to detect novel invasive species.  One source of invasive species passage is plant nurseries. Multiple sources studying invasive species across the world have noted they have played a major role in various A. sagrei invasions.

At our sites we found plant nurseries at three out of the five survey locations. Anolis sagrei was first detected during an invasive lizard survey in which we (Lelani Del Pinto and Samuel Fisher) were determining the spread of parthenogenetic whiptails (Aspidoscelis sonorae) from Arizona, when we stumbled upon the unexpected A. sagrei population.  A new survey began immediately among a tiny strip mall and not one but approximately 30 A. sagrei were seen.

With a new mission in hand, we next turned to iNaturalist which showed a few scattered records of A. sagrei across Orange County. None of the citizen records were from the strip mall at which we conducted our first survey. Doing a literature search, we found one short note about A. sagrei in California, but no other publications for the state. We established five separate sites based on iNaturalist records as well as the other population we found. After that we surveyed all of the sites and accounted for all of the lizard species seen.

Each site with citizen records proved to have at least a couple of hectares of invaded A. sagrei land. Our methodology was focused on trying to understand the total distance the separate A. sagrei populations had spread; by trying to create a minimum convex polygon, we hoped to get an idea about the minimum size of each of these disjunct populations.

As we were already keeping track of all lizard species we found, we quickly noticed a somewhat problematic trend. It seemed that in localities where A. sagrei was present, the native Sceloporus occidentalis was nowhere to be found. Due to the lack of presence of S. occidentalis in the surveyed sites in which A. sagrei was observed, we think there is reason to pursue further surveying to ensure our native western fence lizard is not threatened by this invader.

While the full extent of the invasion is yet to be determined, further studies could prove the issue is more problematic than anticipated, especially if more A. sagrei come into California and eventually establish through the help of the nursery trade. Secondly any downstream effects caused by invasive A. sagrei should be closely watched because extirpations of S. occidentalis may prove troublesome. Sceloporus occidentalis is known to have an important role in our ecosystem and reduces lyme disease.

The results of our study help to show that within southern California, A. sagrei has the potential to become an invader as it has in many other places such as Florida, Hawaii, and Texas. The impact of the potential A. sagrei invasion in southern California will hopefully be further studied and handled appropriately.  We hope you check our paper out to learn the details about where brown anoles have recently spread!

References                                

Fisher SR, Del Pinto LA, Fisher RN. 2020. Establishment of brown anoles (Anolis sagrei) across a southern California county and potential interactions with a native lizard species. PeerJ 8:e8937 https://doi.org/10.7717/peerj.8937

Mahrdt CR, Ervin EL, Nafis G. 2014. Geographic distribution: Anolis sagrei (Cuban Brown Anole). Herpetological Review 45:658–659.

 

Hurricane-blown Anoles are a NY Times Cartoon!

Communicating anole science to the public recently reached dizzy new heights as anoles were immortalized in a New York Times cartoon!

Scientists studying lizards in the Americas found that populations in regions battered by hurricanes have larger toe pads that help them hang on in high wind. It’s proof that extreme weather events can alter the course of a species.” Artist: James Yang

 

The cartoon was published in relation to a recent study in PNAS investigating how hurricanes may drive the evolution of anole toepads by Colin Donihue et al.

Dewlap Size and Seasonality in Mexican Anoles

Figure 1. Some examples of “typical” species found in seasonal and aseasonal environments in Mexico. Please forgive the terrible lighting of the Seasonal photos.

Reprinted from the pages of BioMH: Biology of Mexican Herps:

In 1984, Henry Fitch and David Hillis published a paper on mainland anoles that grabbed my attention decades later as I began my graduate research. In that paper, they described a number of dewlap traits and found that many dewlap scale traits were useful for species identification. They also found an interesting correlation between male dewlap size and habitat type. Species with large male dewlaps were associated with habitats in highly seasonal environments such as deserts and thorn-scrub, while those with small male dewlaps inhabited cloud forests and tropical rainforests (Fig. 1). Why might such an association exist?

Fitch and Hillis proposed a sexual selection hypothesis to explain the pattern. After all, Fitch had previously found decreased sexual size dimorphism (SVL) in anole species associated with stable environments such as cloud forests and rainforests (1976). One interpretation of this pattern is that the intensity of sexual selection is reduced in species that can breed throughout the year, decreasing body size dimorphism between the sexes. Fitch and Hillis also found increased body size dimorphism in species that had large dewlaps and lived in seasonal environments (1984). Since anoles living in highly seasonal environments can have shortened breeding seasons linked to precipitation (Fleming & Hooker 1973), the Fitch-Hillis Hypothesis posits that constraints in length of the breeding season increases male dewlap size due to strengthened sexual selection (1984).

Using new datasets for Mexican anoles, we re-investigated support for the Fitch-Hillis Hypothesis at two scales. We performed “macro” analyses across over 40 Mexican anole species and also looked at the Anolis sericeus group, the only group that occurs broadly throughout seasonal and aseasonal habitat types. In our study, we were able to do two important things differently than the original study. The first is that we were able to treat seasonality as a continuous variable thanks to modern GIS tools and environmental data (Hijmans et al. 2005), enabling a finer-scale look at the link between male dewlap size and seasonality. The original study treated seasonality as a categorical variable (“seasonal” vs “aseasonal”). The second difference is that we were able to correct for phylogenetic non-independence of species. To put it simply, species may be similar in dewlap size due to relatedness to other species (evolutionary history) rather than to the seasonality environment they inhabit. To do this, we used a recently-published phylogeny (Poe et al. 2017) and phylogenetic regression (PGLS) to verify the results of the previous study.

Interestingly enough, our standard ordinary least squares (OLS) regression analyses duplicated results from the original study; without accounting for evolutionary history, there is indeed a strong correlation between male dewlap size and seasonality in Mexican anoles (Fig. 2A, black line). Being able to replicate results using different datasets and approaches is very important and not as common as many of us scientists would like. However, as reflected in the more flattened red dotted line in the figure below, the correlation is weakened substantially after accounting for phylogeny. We therefore cannot say with confidence that seasonality affects male dewlap size in Mexican anoles.

Figure 2. Regression results from Gray et al. (2020). (A) Results from our “macro” analyses, with black line representing standard OLS regression results and red dotted line representing the PGLS results. (B) Results for the Anolis sericeus complex, with black line representing results for all three major lineages and red dotted line representing results of the Pacific and Caribbean lineages. See paper for further details or please ask questions in the comment section below!

We were not able to perform phylogenetic regressions on the Anolis sericeus complex, unfortunately. Though several of us published a phylogeographic study on the silky anoles, many populations represented in the dewlap dataset were not included in that work (Gray et al. 2019). Therefore we had to come up with another way to investigate a correlation in silky anoles. Our phylogeographic work discovered three clades which we assigned Pacific, Caribbean, and Yucatan. Incidentally, the Yucatan lineage is diagnosed in part by small male dewlap size (Lara-Tufiño et al. 2016). The Yucatan lineage also occurs in relatively aseasonal environments that fall within the conditions inhabited by the Caribbean lineage (Gray et al. 2020). So after running regressions on all populations (Fig. 2B, black line), we also ran regressions on only the Pacific and Caribbean lineages, which collectively experience the broadest range of seasonality environments (Gray et al. 2020). As you can see in the figure above, removing the Yucatan lineage flattens the regression line and makes it clear the correlation between male dewlap size and seasonality in silky anoles is influenced by phylogenetic history (Fig. 2B, red dotted line).

Does this mean seasonality is not a driver of male dewlap size? Not necessarily. We discuss other possibilities in the paper, including that anole lineages in Mexico may not have “switched” environments enough for us to be able to detect an effect. We found strong phylogenetic signal for seasonality in Mexican anoles, suggesting species from lineages preferring seasonal environments do not often switch to aseasonal environments and vice versa. As an example, one lineage of 14 west Mexican anoles consists of species that tend to have large dewlaps and live in seasonal environments. In that clade, having a large dewlap might be traceable to one evolutionary event when the most recent common ancestor of the clade evolved a large dewlap. Sexual selection and a truncated breeding season might have had something to do with that event…or the ancestor may have evolved a large dewlap for other reasons and extant species maintained the trait.

While the final result may not be super exciting, I enjoyed working on this project. Collectively, I spent about one year in Mexico catching lizards during grad school and our sample size for some species still left a lot to be desired. Datasets like this take a lot of time and effort to generate! A lot of friends and collaborators helped find and photograph animals through the years. I want to thank Adam Clause, Luke Mahler, Eric Schaad, and Britt White for taking some of the best dewlap photos in our collection.

If anyone wants to play around with the data, they are available at Dryad. And the paper is open access and short, so check it out!

References

Fitch HS (1976) Sexual differences in the mainland anoles. Occasional papers of the Museum of Natural History, the University of Kansas, 50:1-21.

Fitch HS, DM Hillis (1984) The Anolis dewlap: Interspecific variability and morphological associations with habitat. Copeia, 1984:315-323.

Fleming TH, RS Hooker (1973) Anolis cupreus: the response of a lizard to tropical seasonality. Ecology, 56:1243-1261.

Gray LN, AJ Barley, S Poe, RC Thomson, A Nieto-Montes de Oca, IJ Wang (2019) Phylogeography of a widespread lizard complex reflects patterns of both geographic and ecological isolation. Molecular Ecology, 28:644-657.

Gray LN, AJ Barley, DM Hillis, CJ Pavón-Vázquez, S Poe, BA White (2020) Does breeding season variation affect evolution of a sexual signaling trait in a tropical lizard clade? Ecology and Evolution, 10:3738-3746.

Hijmans RJ, SE Cameron, JL Parra, PG Jones, A Jarvis (2005) Very high resolution interpolated climate surfaces for global land areas. International Journal of Climatology, 25:1965-1978.

Lara-Tufiño JD, A Nieto-Montes de Oca, A Ramírez-Bautista, LN Gray (2016) Resurrection of Anolis ustus Hallowell, 1856 (Squamata, Dactyloidae). Zookeys, 2016:147-162.

Poe S, A Nieto-Montes de Oca, O Torres-Carvajal, K de Queiroz, JA Velasco, B Truett, LN Gray, MJ Ryan, G Kohler, F Ayala-Varela, I Latella (2017) A phylogenetic, biogeographic, and taxonomic study of all extant species of Anolis (Squamata: Iguanidae). Systematic Biology, 66:663-697.

Helminths Associated with Anolis fuscoauratus in Highland Marshes of the Brazilian Semi-Arid Region

New literature alert!

In Journal of Helminthology
dos Santos Mesquita, de Oliveira, Perez, and Ávila

Abstract

Helminthological studies may contribute with valuable information on host biology and conservation. Herein, we provide new data on helminths infecting the lizard Norops fuscoauratus, testing one of the factors considered most important in parasitic ecology: host size. We analysed 25 specimens of N. fuscoauratus from three highland marshes in the Brazilian semi-arid. Eight taxa of helminths belonging to Nematoda, Trematoda and Acanthocephala were found. Physaloptera sp. showed the higher prevalence (40%), with a mean intensity of infection of 3.3 ± 1.46 (1–16) and mean abundance 1.32 ± 0.65 (0–16). Norops fuscoauratus represents four new host records for the helminths Cyrtosomum sp., Pharyngodon travassosiStrongyloides sp. and Centrorhynchus sp. There is no relationship of host body size (P = 0.79) and mass (P = 0.50) with parasite richness. In addition, the present study contributes to the knowledge of the parasitic fauna of N. fuscoauratus and the Neotropical region.

Read the full article here!

Free Online Course: Landscaping for Lizards

On Wednesday, May 20 at 4:00PM EDT, the University of Florida IFAS Extension Service is hosting a free online course! Here’s the event description from the website.

Learn about how you can landscape for lizards! We will cover many of the species you may see in Northeast Florida, the many benefits to having them around, and what you can do you in landscape and garden to support and protect them.

This is a free online course but registration through Eventbrite is required and the class is limited in size to 80 participants.

The cover photo for the event features a green anole (Anolis carolinensis, also pictured above), so expect some discussion of our beloved anoles. If you attend, please comment below and let us know what you learned!

You can register for the course here.

Anoles Love It When Ant and Termite Nests Get Opened

Lepidoterist and keen naturalist Andrei Sourakov from the Florida State Museum posted this photo on Twitter.

This is actually an effective, if somewhat mean to the little insects, way of watching anoles, as Stan Rand noted in his 1975 paper of A. agassizi: “In the West Indies, a well-established method for attracting large numbers of anoles is to break open a termite nest. Under such conditions, large numbers will often gather and feed actively with little aggressive interaction.”

 

Another Great Anole Journal Cover!

Another one bites the dust for Team Anole! The cover image of the most recent issue of the Proceedings of the National Academy of Sciences is a beautiful green anole (Anolis carolinensis), which accompanies a study in the same issue investigating the evolutionary effects of hurricanes on anole toepads by Colin Donihue et al.

Congrats too to Neil Losin for taking this fabulous photo!

Donihue, C.M., Kowaleski, A.M., Losos, J.B., Algar, A.C., Baeckens, S., Buchkowski, R.W., Fabre, A.C., Frank, H.K., Geneva, A.J., Reynolds, R.G., Stroud, J.T., Velasco, J.A., Kolbe, J.J., Mahler, D.M., Herrel, A. 2020. Hurricane effects on Neotropical lizards span geographic and phylogenetic scales. Proceedings of the National Academy of Sciences, 117 (19): 10429-10434

Biological Invasions Lead to Increased Aggressiveness in Endemic Lizards

Male of A. oculatus (background), displaying to the conspecific robot (foreground). Credit: Claire M.S. Dufour

Invasive species can have large negative effects on the environment and the economy, and this is a major driver of research interest. We want to understand what makes invasive species succeed or fail, so that we can tip the balance in favor of native counterparts. Increasingly, biological invasions are also recognized for their research value. These “accidental experiments” can help us answer questions about community assembly, species interactions and evolution (Losos et al. 1993; Stuart et al. 2014; Stroud 2019).

Much of the research on introduced species has focused on obtaining information that can help us predict the next invasion event. This includes efforts to understand pathways of invasion (which can be done using population genetic data) or to identify the traits that make invasive species so successful (which can be done by comparing invasive and non-invasive taxa). Less research has focused on what happens shortly after an invasive species gains a foothold. In particular, we know little about early behavioral interactions between invasive and native species. Might these exchanges determine invasion outcomes and patterns of spread?

Enter the anoles of Dominica

In a recent paper, Dufour and collaborators address this gap using native and invasive anoles in Dominica. The authors built lizard robots that mimic the morphology and display behavior of the invasive species (A. cristatellus) and the endemic species (A. oculatus). With these robots, they tested the responses of A. oculatus males when presented with conspecific and heterospecific displays. The authors used sites where both species are found, and sites where only the endemic is found. Therefore, they could contrast the responses of A. oculatus with and without prior experience with the invader.

Interspecific fight between A. oculatus (left) and A. cristatellus (right). Credit: Claire M.S. Dufour

Robots elicited the expected response. In addition, A. oculatus could discriminate a conspecific robot from a heterospecific robot. Intriguingly, a response to heterospecific displays was recorded even in A. oculatus populations with no prior experience with A. cristatellus. This finding is surprising given the lack of shared evolutionary history of the two species, and remains to be explained. Lastly, A. oculatus males that co-occur with A. cristatellus had a more aggressive display response.

A. oculatus are typically larger and are expected to be the dominant species during aggressive encounters (Dufour et al. 2018a,b). Therefore, it is possible that observed behavioral shifts will impact species coexistence and ultimately decide the long-term outcome of this invasion. Read all about Claire’s exciting new study!

 

Hot Nests and Thermal Stress: Why Do Animals Die when They Get Hot?

A hatching brown anole.

Temperature is probably the most studied environmental factor that influences living things; however, you might be surprised to learn that we still don’t have a solid understanding of why things die when they get hot. If you recall your intro biology, you’ll remember that proteins and cell membranes fall apart when they get hot, and that is often the explanation for death at high temperatures. But, there are several reasons to question this explanation. For example, complex organisms (e.g. plants and animals) universally have lower heat tolerance than simple organisms (e.g. bacteria), despite using the same basic biochemical building blocks (i.e. proteins and membranes). Moreover, complex organisms often die at temperatures lower than those that cause proteins and membranes to fall apart.

One explanation has gained a lot of traction in recent years: the oxygen-and capacity-limited thermal tolerance concept (what a mouth full!). This concept posits that as your body heats up, you need more oxygen; however, you eventually get so hot that you can’t get enough oxygen to survive.  There is growing evidence that oxygen limitation explains thermal tolerance for reptile eggs. Several studies show that when eggs are incubated in low oxygen conditions, their heat tolerance is lower (e.g. Smith et al., 2015); however, we still don’t know much about embryo metabolism at near-lethal temperatures, which would vastly improve our understanding of embryo heat tolerance.

In a recent study (Hall and Warner, 2020), we (I and Dr. Dan Warner, who was recently awarded the distinction of “Outstanding Mentor” by Auburn University – well deserved) sought to better understand the factors that determine heat tolerance of reptile embryos. We used eggs from our good friend, the brown anole (Anolis sagrei). Using 1-hour heat shocks, we measured the lethal temperature of embryos (~45.3 °C). We then monitored heart rate and metabolism of eggs across temperature, including near-lethal temperatures.

Figure 1. Heart rate of brown anole eggs across temperature.

As embryos approach the lethal temperature, heart rate and CO2 production increase (Figure 1), but oxygen consumption plateaus (Figure 2). Therefore, eggs need more and more energy as they heat up, but they are eventually unable to support their energy needs via aerobic respiration. Without enough oxygen, energy production is less efficient. These data indicate that oxygen is limited at near-lethal temperatures and provides additional support for the oxygen-and capacity-limited thermal tolerance concept for reptile eggs.

Figure 2. Oxygen consumption across temperature for brown anole eggs.

Many aspects of human-induced global change cause increases in temperature (e.g. deforestation, urbanization, climate change), potentially heating lizard nests and exposing embryos to thermal stress. The results of our study make progress toward understanding how embryos respond to extreme temperatures, which is important to understand how reptile populations will respond to global change.

Hall, J.M. and Warner, D.A., 2020. Thermal sensitivity of lizard embryos indicates a mismatch between oxygen supply and demand at near-lethal temperatures. Journal of Experimental Zoology, in press. https://doi.org/10.1002/jez.2359

Smith, C., Telemeco, R.S., Angilletta Jr, M.J. and VandenBrooks, J.M., 2015. Oxygen supply limits the heat tolerance of lizard embryos. Biology letters11(4), p.20150113.

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