Fine-scale dispersal in a stream caddisfly inferred from spatial autocorrelation of microsatellite markers

Abstract

Most population genetic studies in streams infer long-term patterns of gene flow by calculating fixation indices (e.g., F ST ) among sampled populations. In more-recent analytical methods, the need to assign individuals to populations a priori (clustering algorithms) is relaxed, and spatial autocorrelation analysis of allele frequencies (SA) is used to infer finer-scale and potentially short-term dispersal distances. We applied multiple methods to study the population genetic structure of the riverine caddisfly Stenopsyche marmorata (Trichoptera:Stenopsychidae) from 4 adjacent catchments in northeastern Japan. We genotyped larval individuals (N = 532) from 30 sites at 8 polymorphic microsatellite loci. Fixation indices suggested low levels of genetic differentiation among populations (global F ST = 0.062, p < 0.01), and significant isolation-by-distance (IBD) indicated populations were in drift-migration equilibrium. Bayesian clustering separated S. marmorata into distinct upland (>250 m asl) and lowland populations, with different F ST values (upland F ST = 0.048, p < 0.01; lowland F ST = 0.029, p < 0.01) and significant IBD only among upland populations. Allele frequencies were significantly positively autocorrelated (Moran's I > 0, p < 0.05) at distances up to 18 km along streams and up to 12 km across terrestrial habitat. These values were similar to directly observed flight distance in a single generation for this species in the field. We conclude that the multiple-method approach revealed: 1) unexpected population subdivision between upland and lowland areas that may result from local adaptation, differences in phenology, and historical colonization by multiple lineages; and 2) fine-scale estimates of dispersal that match direct observations of flight and suggest gene flow is more pronounced along water courses in this species.

Geomorphic influence on intraspecific genetic differentiation and diversity along hyporheic corridors

“…These low levels of genetic differentiation and large cluster sizes are comparable with those reported for aquatic insects achieving downstream drift and adult flight (e.g. caddisflies; Yaegashi, Watanabe, Monaghan, & Omura, ). This suggests widespread gene flow in the hyporheic corridor, with isolation by distance occurring at a scale of tens of kilometres.…”

“…Also, the pattern of higher genetic differentiation among upstream demes than downstream demes and smaller STRUCTURE cluster size in upstream reaches (see Figure ) is proposed to reflect increased geomorphic constraints to the migration of P. walteri in steep slope channels that accumulate thinner and more discontinuous alluvial deposits. A greater genetic structure among upstream populations of surface aquatic organisms has long been considered as a general spatial pattern (Hughes, ; Hughes et al., ; Storfer, Murphy, Spear, Holderegger, & Waits, ; Yaegashi et al., ; but see Paz‐Vinas et al., ). Here, we provide the first evidence that this pattern also applies to interstitial organisms and that it varies in magnitude among river corridors.…”

Evaluating the impact of a fluoropolymer plant on a river macrobenthic community by a combined chemical, ecological and genetic approach

“…Indeed, many studies demonstrated the presence of low divergence between aquatic insect species, with a typical pattern of higher variability within than between populations (Alp et al, 2012;Paris et al, 2010;Sivaramakrishnan et al, 2014;Yaegashi et al, 2014), as also found in this case. Moreover, spatial autocorrelation of genetic variability along rivers for a trichopteran species was estimated to persist in a range of 12-18 km (Yaegashi et al, 2014), which roughly corresponds to the estimated flight dispersal of the species and by far longer than the distance (1 km) between the two stations studied in the river Bormida. All this suggests that other factors than geographical isolation or distance may be considered to explain the evidenced divergence in the case of the populations of H. modesta of the Bormida.…”

Local population genetic structure of the montane caddisfly Drusus discolor is driven by overland dispersal and spatial scaling

“…Previous population genetic studies of headwater insect species have mainly used DNA sequencing and AFLPs to assess regional patterns and revealed strong catchment differentiation (e.g. Hughes et al ., ; Wishart & Hughes, ; Lehrian et al ., ; Yaegashi et al ., ), strong differentiation within catchments (Monaghan et al ., ) or variation among codistributed taxa (Monaghan et al ., ; Sabando et al ., ). A few examples also show effective dispersal with limited population structure (e.g.…”