Foraging decisions shape the structure of food webs. Therefore, a behavioral shift in a single species can potentially modify resource-flow dynamics of entire ecosystems. To examine this, we conducted a field experiment to assess foraging niche dynamics of semi-arboreal brown anole lizards in the presence/absence of predatory ground-dwelling curly tailed lizards in a replicated set of island ecosystems. One year after experimental translocation, brown anoles exposed to these predators had drastically increased perch height and reduced consumption of marine-derived food resources. This foraging niche shift altered marine-to-terrestrial resource-flow dynamics and persisted in the diets of the first-generation offspring. Furthermore, female lizards ¬¬that displayed more risk-taking behaviors consumed more marine prey on islands with predators present. Our results show how predator-driven rapid behavioral shifts can alter food-web connectivity between oceanic and terrestrial ecosystems and underscore the importance of studying behavior-mediated niche shifts to understand ecosystem functioning in rapidly changing environments.

Introductions of invasive species to new environments often result in rapid rates of trait evolution. While in some cases these evolutionary transitions are adaptive and driven by natural selection, they can also result from patterns of genetic and phenotypic variation associated with the invasion history. Here, we examined the brown anole (Anolis sagrei), a widespread invasive lizard for which genetic data have helped trace the sources of non-native populations. We focused on the dewlap, a complex signaling trait known to be subject to multiple selective pressures. We measured dewlap reflectance, pattern, and size in 30 non-native populations across the southeastern United States. As well, we quantified environmental variables known to influence dewlap signal effectiveness, such as canopy openness. Further, we used genome-wide data to estimate genetic ancestry, perform association mapping, and test for signatures of selection. We found that among-population variation in dewlap characteristics was best explained by genetic ancestry. This result was supported by genome-wide association mapping, which identified several ancestry-specific loci associated with dewlap traits. Despite the strong imprint of this aspect of the invasion history on dewlap variation, we also detected significant relationships between dewlap traits and local environmental conditions. However, we found limited evidence that dewlap-associated genetic variants have been subject to selection. Our study emphasizes the importance of genetic ancestry and admixture in shaping phenotypes during biological invasion, while leaving the role of selection unresolved, likely due to the polygenic genetic architecture of dewlaps and selection acting on many genes of small effect.

Introductions of invasive species to new environments often result in rapid rates of trait evolution. While in some cases these evolutionary transitions are adaptive and driven by natural selection, they can also result from non-adaptive processes associated with the invasion history. Here, we examined the role of adaptive and non-adaptive evolutionary processes in the brown anole (Anolis sagrei), a widespread invasive lizard for which genetic data have helped trace the sources of non-native populations. We focused on the dewlap, a signaling trait known to be subject to multiple selective pressures. We measured dewlap reflectance, pattern, and size in non-native populations across the southeastern United States. We combine these trait measurements with quantification of environmental variables known to influence dewlap signal effectiveness, such as canopy openness. Further, we use genome-wide data to estimate ancestry and to perform association mapping for dewlap traits. We found that among-population variation in dewlap characteristics is best explained by ancestry, as contributed by invasion history. This result was supported by genome-wide association mapping, which identified several ancestry-specific loci associated with dewlap traits. Despite the strong imprint of invasion history on dewlap variation, we also detect significant relationships between dewlap traits and local environmental conditions. Thus, our results are also consistent with natural selection influencing trait evolution during the brown anole invasion. Our study clarifies the importance of ancestry and admixture in shaping phenotypes during biological invasion, while also showing that some traits can respond adaptively to conditions encountered in the invasive range despite potential constraints imposed by invasion history.

Invasive species can impact native populations through competition, predation, and habitat alteration, but also genetically through hybridization. Potential outcomes of hybridization span the continuum from extinction to hybrid speciation and can be further complicated by anthropogenic habitat disturbance. Hybridization between the native green anole lizard (Anolis carolinensis) and a morphologically similar invader (A. porcatus) in south Florida provides an ideal opportunity to study interspecific admixture across a heterogeneous landscape of urban and forested habitats. We used reduced-representation sequencing to describe introgression in this hybrid system and to test for a relationship between urbanization and invasive ancestry. Our findings indicate that hybridization between green anole species was likely a limited, historic event, and that patterns of backcrossing have produced two distinct genetic clusters within the hybrid population. Genomic cline analyses revealed rapid introgression and disproportionate representation of invasive alleles at many loci, and no evidence for reproductive isolation between the two species. We also found a positive relationship between urbanization and invasive ancestry, although the mechanism driving this association remains unclear. Ultimately, our findings demonstrate the persistence of non-native genetic material even in the absence of ongoing immigration, indicating that selection favoring invasive alleles can override the demographic limitation of low propagule pressure. However, we also note that not all outcomes of admixture between native and invasive species should be considered intrinsically negative. Hybridization with ecologically robust invaders can lead to adaptive introgression, which may facilitate the long-term survival of native populations otherwise unable to adapt to anthropogenically mediated global change.