Species-level diversification (speciation) results from the evolution of reproductive isolation. When reproductive isolation is intrinsic (independent of ecological context), speciation is thought to be irreversible. Intrinsic reproductive isolation manifests as a reduction in hybrid fitness due to Dobzhansky-Muller incompatibilities, and can render hybrids sterile or inviable. During fieldwork in western Cuba, I identified abnormal-looking individuals with small gonads within an assemblage of Anolis. I hypothesized that such individuals were interspecific hybrids and predicted a phenotypic distinctness and lower reproductive fitness. I evaluated my predictions by comparing putative hybrids with candidate parental species in external phenotypic traits and gonadal indicators of reproductive fitness. I found that putative hybrids were phenotypically distinct and did not produce sperm cells, suggesting that hybrid sterility may be important in maintaining species boundaries in this ecologically complex system.

You do not currently have access to this content.