Date of Award

2021

Degree Type

Thesis

Degree Name

Master of Science in Biological and Environmental Sciences (MSBES)

Specialization

Ecology and Ecosystem Sciences

Department

Biological Sciences

First Advisor

Jason J. Kolbe

Abstract

Invasive species impact native biota through competition, predation, and habitat alteration but can also transform native populations through hybridization. Outcomes of such hybridization events are variable and may result in the formation of a stable hybrid tension zone, extinction of one parental species via genetic swamping, hybrid speciation, or adaptive introgression. Hybrid population dynamics are further complicated by anthropogenic habitat disturbance, which has been shown to influence patterns of admixture and introgression between native and invasive species. Hybridization between the native lizard Anolis carolinensis and a morphologically similar invader (A. porcatus) in South Miami, Florida provides an ideal opportunity to study outcomes of admixture across a heterogeneous landscape composed of both urban and forested habitat patches. We used single nucleotide polymorphism (SNP) data to describe patterns of introgression occurring in the A. carolinensis x A. porcatus hybrid system, as well as to test for a relationship between urbanization and non-native ancestry. Our findings indicate that hybridization between A. carolinensis and A. porcatus was likely a limited, historic event, and that contemporary immigration of A. porcatus is negligible. We identified two distinct genetic clusters within the hybrid population and related these to differences in recent patterns of hybrid backcrossing with A. carolinensis. Investigation of genomic clines revealed rapid introgression and disproportionate representation of A. porcatus alleles at many loci, as well as a total lack of evidence for reproductive isolation between parental species. We also found evidence for a positive relationship between urbanization and A. porcatus ancestry, though 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 hybridization management strategies should focus on preserving native alleles (rather than simply removing invasive individuals) in populations where admixture has already occurred. However, we also note that not all outcomes of interspecific admixture should be considered intrinsically negative. Hybridization of native species with ecologically robust invaders can lead to adaptive introgression, which in turn may facilitate the long-term survival of populations or species otherwise unable to adapt to global, anthropogenically-mediated change.

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