Interaction Cascades in Anthropogenic Glades

Pastoralism was traditionally, and is currently, one of the most pervasive and widespread livelihoods throughout East African savannas. After abandonment, livestock corrals in East African savannas develop into nutrient-rich, treeless “glades” that persist for decades. Other research has shown that glades have significantly higher concentrations of soil nutrients including nitrogen, potassium and carbon, which support several specialist grass species, and turning these patches long-term primary productivity hotspots. Using detailed observations, extensive sampling, and experimental methods, we demonstrate that these effects on primary productivity cascade up two trophic levels to increase abundance of insects and the gecko Lygodactylus keniensis. Extending previous research, we find that Acacia drepanolobium trees close to glade edges are larger and grow faster than those farther from the glade. Furthermore, we demonstrate experimentally that grasshoppers grow significantly faster inside glades than far away from glade edges and that arboreal insect abundance, biomass and diversity show the same significant trend. Finally, we find that geckos are significantly more abundant in trees close to the glade edge than far away. Our results show that traditional pastoral methods have significant impacts on multiple trophic levels at multiple scales and add important habitat heterogeneity to an otherwise homogenous landscape.Master of ScienceNatural Resources and EnvironmentUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/83507/1/Donihue_SNRE_Thesis.pd

Glade cascades: indirect legacy effects of pastoralism enhance the abundance and spatial structuring of arboreal fauna

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/117219/1/ecy2013944827.pd

Chromosome-scale genome assembly of the brown anole (Anolis sagrei), an emerging model species

Rapid technological improvements are democratizing access to high quality, chromosome-scale genome assemblies. No longer the domain of only the most highly studied model organisms, now non-traditional and emerging model species can be genome-enabled using a combination of sequencing technologies and assembly software. Consequently, old ideas built on sparse sampling across the tree of life have recently been amended in the face of genomic data drawn from a growing number of high-quality reference genomes. Arguably the most valuable are those long-studied species for which much is already known about their biology; what many term emerging model species. Here, we report a highly complete chromosome-scale genome assembly for the brown anole, Anolis sagrei – a lizard species widely studied across a variety of disciplines and for which a high-quality reference genome was long overdue. This assembly exceeds the vast majority of existing reptile and snake genomes in contiguity (N50 = 253.6 Mb) and annotation completeness. Through the analysis of this genome and population resequence data, we examine the history of repetitive element accumulation, identify the X chromosome, and propose a hypothesis for the evolutionary history of fusions between autosomes and the X that led to the sex chromosomes of A. sagrei

Data from: Feed or fight: testing the impact of food availability and intraspecific aggression on the functional ecology of an island lizard

Body size often varies among insular populations relative to continental conspecifics – the ‘island rule’ – and functional, context-dependent morphological differences tend to track this body size variation on islands. Two hypotheses are often proposed as potential drivers of insular population differences in morphology: one relating to diet and the other involving intraspecific competition and aggression. We directly tested whether differences in morphology and maximum bite capacity were explained by interisland changes in hardness of both available and consumed prey, and levels of lizard-to-lizard aggression among small-island populations. Our study included 11 islands in the Greek Cyclades and made use of a gradient in island area spanning five orders of magnitude. We focused on the widespread lizard Podarcis erhardii. We found that on smaller islands, P. erhardii body size was larger, head height was larger relative to body size, and maximum bite capacity became proportionally stronger. This pattern in morphology and performance was not related to differences in diet, but was highly correlated with proxies of intraspecific aggression – bite scars and missing toes. Our findings suggest that critical functional traits such as body size and bite force in P. erhardii follow the predictions of the island rule and are changing in response to changes in the competitive landscape across islands of different sizes

Feed or fight: testing the impact of food availability and intraspecific aggression on the functional ecology of an island lizard

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137218/1/fec12550.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137218/2/fec12550-sup-0001-LaySummary.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137218/3/fec12550_am.pd

Body condition and jumping predict initial survival in a replicated island introduction experiment

Over-water dispersal to small islets is an important eco-evolutionary process. Most often, new arrivals on islets find the environment harsh or mate-less, making their footholds on these islets fleeting. Occasionally, introduced animals are able to survive the strong selection following their arrival, leading to subsequent propagation and, in several famous cases, adaptive radiation. What traits predict that initial survival? We established a replicated island introduction experiment to investigate this process in lizards. In 2014, we introduced 20 Podarcis erhardii lizards to each of five small islets in the Greek Cyclades Islands. We found that the lizards that survived were those with better initial body condition, longer distal portions of their limbs and a greater propensity for jumping. Contrary to our expectations, neither body size nor the strength of the lizards' bite - two traits positively related to competitive ability, which becomes important later in the colonization process in lizards - predicted survival. This is the first selection study of its kind investigating an experimental introduction of Podarcis, and whether the traits that determined initial survival are important in driving the future evolutionary trajectories of these populations remains to be determined

An aerodynamic perspective on hurricane-induced selection on Anolis lizards

International audienceStudies have demonstrated that hurricanes can drive selection in Neotropical anoles. In a recent study, it was shown that post-hurricane survivors showed longer toepad areas and, surprisingly, shorter femurs.One potential explanation for the reduction in femur length is that increased drag on individuals with longer femurs causes them to be blown off their perch. Consequently, lizards with shorter femora might survive better in hurricanes.To gain insight into the form–function relationships of drag reduction in perched lizards exposed to high-velocity winds, we quantified drag forces on Anolis lizard models in realistic grasping positions using computational fluid dynamics.We showed that overall drag, as well as the relatively high drag at the hindlimbs strongly increase with the distance of the pelvic region from the perch. As optimal postures to resist sustained arboreal pulling involve extended limbs, longer hindlimbs increase the chance of having the limbs and pelvic region positioned outside the zone in which efficient shielding from the wind by the perch occurs.Our study underlines the complexity of performance trade-offs on the evolution of limb morphology in arboreal lizards, and emphasizes the importance of generally ignored functions such as aerodynamic drag reduction in arboreal ecosystems

Donihue et al. 2015 Feed or Fight Data

All data archived here were used for analyses in Donihue et al. "Feed or Fight: Testing the impact of food availability and intraspecific aggression on the functional ecology of an island lizard." Data is in five worksheets. Please see ReadMe file for additional information