Meeting Abstract
Changes in morphological diversity among populations are possible when the environmental conditions of one population’s habitat shift via either natural or anthropogenic causes. Recently, we collected data suggesting that a population of Amargosa pupfish Cyprinodon nevadensis amargosae in an isolated thermal spring in the Death Valley region, USA, experienced a contemporary change in body morphology related to alterations to the physical structure and thermal regime of their habitat. Collections of fish from the thermal spring’s outflow channel and associated marsh in 2007-2008 indicated that fish in this isolated thermal spring habitat exhibited a similar distribution of body sizes as conspecifics in the nearby Amargosa River. Collections of pupfish from these same allopatric populations in 2013-14, however, revealed a shift in both the body size and morphological shape of pupfish occupying the thermal spring habitat. These collections indicated that pupfish in this habitat were now on average 12.3% smaller in body length and 48.1% less in mass than in 2008. These collections also revealed that 33.8% of pupfish within the thermal spring population now exhibit either complete or partial (only 1 pelvic fin) loss of the paired pelvic fins. This finding contrasts with greater than 99% of pupfish having both pelvic fins in this habitat in 2008, as well as in the nearby Amargosa River population. Landmark-based, geometric morphometric analyses further revealed differences in body depth between the thermal spring and Amargosa River populations. Body depth is a sexually dimorphic trait in Cyprinodon spp. with males exhibiting deeper bodies than females; the thermal spring population, however, shows a distinct reduction in body depth sexual dimorphism compared to the Amargosa River population.
