Abstract
BackgroundContemporary evolution following assisted colonization may increase the probability of persistence for refuge populations established as a bet-hedge for protected species. Such refuge populations are considered “genetic replicates” that might be used for future re-colonization in the event of a catastrophe in the native site. Although maladaptive evolutionary divergence of captive populations is well recognized, evolutionary divergence of wild refuge populations may also occur on contemporary time scales. Thus, refuge populations may lose their “value” as true genetic replicates of the native population. Here, we show contemporary evolutionary divergence in body shape in an approximately 30-year old refuge population of the protected White Sands pupfish (Cyprinodon tularosa) resulting in a body-shape mismatch with its native environment.Methodology/Principal FindingsGeometric morphometic data were collected from C. tularosa cultures raised in experimental mesocosms. Cultures were initiated with fish from the two native populations, plus hybrids, in high or low salinity treatments representing the salinities of the two native habitats. We found that body shape was heritable and that shape variation due to phenotypic plasticity was small compared to shape variation due to population source. C. tularosa from the high salinity population retained slender body shapes and fish from the low salinity population retained deep body shapes, irrespective of mesocosm salinity. These data suggest that the observed divergence of a recently established pupfish population was not explained by plasticity. An analysis of microsatellite variation indicated that no significant genetic drift occurred in the refuge population, further supporting the adaptive nature of changes in body shape. These lines of evidence suggest that body shape divergence of the refuge population reflects a case of contemporary evolution (over a 30-year period).Conclusions/SignificanceThese results suggest assisted colonization can introduce novel, and/or relaxed selection, and lead to unintended evolutionary divergence.
Highlights
Contemporary evolution has important implications for conservation biology, as the same anthropogenic factors driving the current extinction crisis have been shown to be associated with a variety of cases of contemporary evolution [1,2,3,4]
Our results suggest that evolutionary divergence can occur within decades of population establishment
The observed divergence of the Mound Spring population was more than twice the divergence predicted from phenotypic plasticity
Summary
Contemporary evolution has important implications for conservation biology, as the same anthropogenic factors driving the current extinction crisis have been shown to be associated with a variety of cases of contemporary evolution (evolution over one to a few hundred generations) [1,2,3,4]. Two native populations occur at Malpais Spring and Salt Creek, presumably isolated following the desiccation of Pleistocene Lake Otero approximately 3,000 to 5,000 years ago [15,16] These two populations occupy very different habitats, especially in terms of salinity and water flow. Contemporary evolution following assisted colonization may increase the probability of persistence for refuge populations established as a bet-hedge for protected species Such refuge populations are considered ‘‘genetic replicates’’ that might be used for future re-colonization in the event of a catastrophe in the native site. We show contemporary evolutionary divergence in body shape in an approximately 30-year old refuge population of the protected White Sands pupfish (Cyprinodon tularosa) resulting in a body-shape mismatch with its native environment
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