Phenotypic differentiation in a heterogeneous environment: morphological and life‐history responses to ecological gradients in a livebearing fish

Abstract

Predicting how environmental variation drives phenotypic diversification is one of the main aims of evolutionary ecology. Yet, we still only have a limited understanding of how it drives diversity, especially when multiple factors interact. To address this issue, the superfetating livebearing fish Phalloptychus januarius (Poeciliidae) was repeatedly sampled (over a 2-year period) in four coastal lagoons in Brazil to investigate the relative contribution of different environmental factors on phenotypic patterns. We further compare our results to those reported for another poeciliid (Poecilia vivipara), which inhabits some of the same lagoons but has a drastically different reproductive strategy (no superfetation). We used a model-averaging approach to estimate the relative importance of differences in predation pressure, salinity, dissolved oxygen, pH, temperature and food availability in driving variation in body shape, life histories, and life-history proxies. We found consistent population differences in several traits, but also seasonal variation within each lagoon. Specifically, predation, oxygen availability and pH affected several different traits and played important roles in driving phenotypic differences between and amongst populations. Moreover, our study reveals differential responses in phenotypic traits to the same environmental gradients between P. januarius (this study) and P. vivipara (previous studies), and we suggest that future work should further investigate differential phenotypic responses to single versus multiple concomitant selective forces, and how this affects different species.

Predation and Resource Availability Interact to Drive Life-History Evolution in an Adaptive Radiation of Livebearing Fish

“…Livebearing fishes (family Poeciliidae), such as guppies, mollies, swordtails, and mosquitofish, have been at the forefront of the development of life-history theory (e.g., Reznick and Endler, 1982;Reznick et al, 1990Reznick et al, , 2002Johnson, 2001;Johnson and Belk, 2001;Bronikowski et al, 2002;Jennions and Telford, 2002;Jennions et al, 2006;Riesch et al, 2014Riesch et al, , 2015Moore et al, 2016;Belk et al, 2020;Santi et al, 2020). One especially powerful model system of livebearing fish is the post-Pleistocene radiation of Bahamas mosquitofish (Gambusia hubbsi), as the system offers the opportunity to isolate the effects of predation risk and resource availability on life-history trait evolution.…”

Maternal food restriction during pregnancy affects offspring development and swimming performance in a placental live-bearing fish

“…The P. januarius used in this experiment were laboratory born and derived from laboratory stocks originally collected in the Rodrigo de Freitas Lagoon, Rio de Janeiro (Brazil) in November 2006 and held at the Pollux lab (Wageningen University, the Netherlands). In the Rodrigo de Freitas lagoon, P. januarius co-occurs with a variety of piscivorous fish ( Andreata, 2012 ), birds ( Santi et al, 2020 ) and bats ( Luz et al, 2011 ), which collectively may represent a predation risk. Moreover, in their natural habitat they may experience both intra- and interspecies competition for food.…”

“…Besides intrinsic trade-offs and constraints, resource allocation, and hence, life-histories are influenced by environmental factors, such as food availability (Boggs, 1992;Santi et al, 2020).…”

“…In addition to intrinsic trade-offs and constraints, resource allocation and hence life-histories are also influenced by environmental factors, such as food availability ( Boggs, 1992 ; Santi et al, 2020 ). Increased maternal food availability enables a higher energy uptake, which can be allocated to any function ( van Noordwijk and de Jong, 1986 ).…”

Life History Divergence in Livebearing Fishes in Response to Predation: Is There a Microevolution to Macroevolution Barrier?

“…Livebearing fishes of the family Poeciliidae have been the subject of numerous studies evaluating the impact of different environments on life history strategies (e.g., [7,8,[13][14][15][16][17][18][22][23][24][25][26]). The effect of divergent predation environments has been of particular interest, with among population patterns of divergence in life history being characterized by a relatively large size at maturity, low reproductive allocation, large offspring size, and low number of offspring in predator-free or low mortality sites contrasted with small size at maturity, high reproductive allocation, small offspring size, and high number of offspring in predator or high mortality sites [22][23][24]27,28].…”