Pelagic larval duration predicts extinction risk in a freshwater fish clade

Abstract

Pelagic larval duration (PLD) can influence evolutionary processes ranging from dispersal to extinction in aquatic organisms. Using estimates of PLD obtained from species of North American darters (Percidae: Etheostomatinae), we demonstrate that this freshwater fish clade exhibits surprising variation in PLD. Comparative analyses provide some evidence that higher stream gradients favour the evolution of shorter PLD. Additionally, similar to patterns in the marine fossil record in which lower PLD is associated with greater extinction probability, we found a reduced PLD in darter lineages was evolutionarily associated with extinction risk. Understanding the causes and consequences of PLD length could lead to better management and conservation of organisms in our increasingly imperiled aquatic environments.

Small fish, large river: Surprisingly minimal genetic structure in a dispersal‐limited, habitat specialist fish

“…Habitat of E. lemniscatum is likely temporally unstable, as the Big South Fork is in a gorge and experiences fast and drastic water‐level changes, leading to periods of high flow that can shift or eliminate E. lemniscatum habitat over time. Loss of riffle‐associated habitat can increase movements in other darters (Roberts & Angermeier, ), so movements of E. lemniscatum from shifting habitats (likely juveniles or adults since larvae become benthic immediately upon hatching; Douglas et al, ; Wallus & Simon, ) could account for the relatively high degree of population connectivity we observed. Thus, we propose that the maintenance of gene flow and evidence of dispersal across the range of E. lemniscatum reflects adaptation to a big river environment with patchy and, possibly, temporally unstable habitats.…”

“…A third objective was to examine whether our system shows the expected patterns of the distribution of genetic diversity in riverine systems (DIGD and increased upstream genetic differentiation). We also provide a baseline understanding of genetic diversity in E. lemniscatum to help guide future conservation decisions, given that the species displays several intrinsic characteristics (habitat specialist, dispersal‐limited, benthic larvae, and small native range) indicative of an elevated extinction risk and vulnerability to anthropogenic habitat fragmentation (Douglas et al, ; Warren et al, ).…”

“…This species is expected to show high levels of genetic structure, even at small spatial scales, since it is a habitat specialist with hypothesized limited dispersal ability (Centeno-Cuadros et al, 2011;Fluker, Kuhajda, & Harris, 2014). It F I G U R E 1 A male Tuxedo Darter (Etheostoma lemniscatum) in breeding coloration (photograph by Matthew R. Thomas) has several features associated with limited dispersal ability: it is a small-bodied, benthic darter (Knouft & Page, 2003) that lacks a swim bladder (Page, 1983), has high reproductive investment (Turner & Trexler, 1998), demersal eggs laid on the undersides of rocks (Eisenhour & Burr, 2000), and benthic larvae (Douglas et al, 2013;Wallus & Simon, 2005). Etheostoma lemniscatum is a habitat specialist of shallow, slow-moving water with cobble or slab-rock substrate, generally located adjacent to and upstream of riffles, and is typically found at depths less than 1 m (Davis & Cook, 2010;Eisenhour & Burr, 2000).…”

“…We also provide a baseline understanding of genetic diversity in E. lemniscatum to help guide future conservation decisions, given that the species displays several intrinsic characteristics (habitat specialist, dispersal-limited, benthic larvae, and small native range) indicative of an elevated extinction risk and vulnerability to anthropogenic habitat fragmentation (Douglas et al, 2013;Warren et al, 2000).…”

Fish Functional Traits Correlated with Environmental Variables in a Temperate Biodiversity Hotspot

“…However, many listed species have very different functional traits and the variation could preclude a general trend, so the trait ‘listed’ may not be meaningful. The addition of functional traits correlated with the likelihood of being imperiled, like pelagic larval duration in darters [77] , may improve a generalizable pattern and guide research into the mechanisms responsible for such correlations. However, knowledge of such life history traits is limited to relatively few species and currently precludes incorporation into community level analyses.…”