Invasive species can impact native populations through competition, predation, habitat alteration, and disease transmission, 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. We used reduced-representation sequencing to describe introgression in this hybrid system and to test for a relationship between urbanization and non-native ancestry. Our findings indicate that hybridization between green anole lineages was probably a limited, historic event, producing a hybrid population characterized by a diverse continuum of ancestry proportions. Genomic cline analyses revealed rapid introgression and disproportionate representation of non-native alleles at many loci and no evidence for reproductive isolation between parental species. Three loci were associated with urban habitat characteristics; urbanization and non-native ancestry were positively correlated, although this relationship did not remain significant when accounting for spatial nonindependence. Ultimately, our study demonstrates the persistence of nonnative genetic material even in the absence of ongoing immigration, indicating that selection favouring non-native alleles can override the demographic limitation of low propagule pressure. We also note that not all outcomes of admixture between native and non-native 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.
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.
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