Human‐induced habitat fragmentation effects on connectivity, diversity, and population persistence of an endemic fish, Percilia irwini, in the Biobío River basin (Chile)

Abstract

An understanding of how genetic variability is distributed in space is fundamental for the conservation and maintenance of diversity in spatially fragmented and vulnerable populations. While fragmentation can occur from natural barriers, it can also be exacerbated by anthropogenic activities such as hydroelectric power plant development. Whatever the source, fragmentation can have significant ecological effects, including disruptions of migratory processes and gene flow among populations. In Chile, the Biobío River basin exhibits a high degree of habitat fragmentation due to the numerous hydroelectric power plants in operation, the number of which is expected to increase following new renewable energy use strategies. Here, we assessed the effects of different kinds of barriers on the genetic structure of the endemic freshwater fish Percilia irwini, knowledge that is critically needed to inform conservation strategies in light of current and anticipated further fragmentation initiatives in the system. We identified eight genetic units throughout the entire Biobío system with high effective sizes. A reduced effective size estimate was, however, observed in a single population located between two impassable barriers. Both natural waterfalls and human‐made dams were important drivers of population differentiation in this system; however, dams affect genetic diversity differentially depending on their mode of operation. Evidence of population extirpation was found in two river stretches limited by upstream and downstream dams. Significant gene flow in both directions was found among populations not separated by natural or anthropogenic barriers. Our results suggest a significant vulnerability of P. irwini populations to future dam development and demonstrate the importance of studying basin‐wide data sets with genetic metrics to understand the strength and direction of anthropogenic impacts on fish populations.

Hydrological connectivity drives longitudinal movement of endangered endemic Chilean darter Percilia irwini (Eigenmann, 1927)

“…A recent work by Valenzuela‐Aguayo et al . (2020) supported this study's results, showing that P. irwini were genetically indistinguishable across the lower and the middle sections of the Malleco. This suggests a constant dispersion between these two reaches, as observed in the results.…”

“…The Malleco River and the Laja River are tributaries of the Biobío River, and they together represent three important branches of the catchment. The movement between tributaries is limited because of the geomorphologic nature of the catchment, and each is known to host genetically isolated populations of P. irwini (Valenzuela‐Aguayo et al ., 2020). Sampling sites were chosen to cover each of these tributaries in continuous sections (without physical barriers such as hydroelectric dams or waterfall), but with different features that could influence fish movements ( i.e ., water extraction, fast flowing riffles).…”

“…Chilean Ministry of the Environment classified P. irwini as an endangered species because of its narrow distribution and degradation of its habitat (Habit & Belk, 2007). Indeed, significant decline in populations of P. irwini has been reported in the Biobío River basin in recent decades due to multiple stressors (Habit et al ., 2006), and more recently due to fragmentation imposed by hydropower dams (Valenzuela‐Aguayo et al ., 2020). Except for a few recent studies on galaxiidae and diplomistidae (Górski et al ., 2018; Oyanedel et al ., 2018; Piedra et al ., 2012), the knowledge of movement patterns of Chilean native fish in general and specifically of P. irwini remains scarce.…”

Historical and Contemporary Diversity of Galaxiids in South America: Biogeographic and Phylogenetic Perspectives

“…The presence of salmonids in Patagonian lakes is not the only factor affecting the ecological and genetic patterns of galaxiids. Dams have also produced great changes in watersheds, and their ecological effects on fishes is well documented (e.g., [72][73][74][75]). As expected, dams can also affect fish genetic diversity patterns, but these are generally manifested only after a time lag that is a function of the life history characteristics of the species of concern, including its generation time and its population effective size [22].…”

Riverscape properties contribute to the origin and structure of a hybrid zone in a Neotropical freshwater fish

“…Thus, although they are very recent, these places may have been responsible for imposing additional physical barriers or habitat disturbances (e.g. changes in river depth, temperature and waterflow), with potential influence on fish population structure (Valenzuela‐Aguayo, McCracken, Manosalva, Habit, & Ruzzante, 2020).…”