We determined genetic variance and gene flow across multiple scales (reaches, tributaries, and catchments) to examine the dispersal ability of the caddisfly, Neothremma alicia in streams along the Wasatch Range in the Rocky Mountains of Utah. Neothremma alicia is one of the most abundant caddisflies in this region. We generated DNA sequence data (mitochondrial COI) from 34 reaches, nested in 15 tributaries distributed across 3 adjacent catchments. We identified 47 haplotypes from a total of 486 individuals. The most abundant haplotype (H1) was found at all sites/reaches and comprised 44% of the total number of individuals sequenced. The remaining rare haplotypes (46) were recently derived from the dominant, H1 haplotype. All of the rare haplotypes were restricted to a single catchment with 81 % restricted to either a single tributary or to two adjacent tributaries. We found the largest FST values among tributaries and the smallest FST values between reaches within tributaries suggesting that dispersal and gene flow is largely confined to within tributaries. This result supports the observation that aerial adults commonly crawl and fly along the stream corridor, especially in deeply incised valleys of mountainous regions. Our analyses show that this population has experienced a bottleneck that may have reduced population genetic variance from many haplotypes to one single dominant haplotype, H1. The rare haplotypes may have diverged since the bottleneck from the H1 haplotype and thus, have not had time to disperse outside their catchment and in most cases outside their specific tributary. Our analyses indicated that the bottleneck took place between 1,000 and 10,000 years ago. Thus, it appears that most rare haplotypes have been unable to colonize outside of the tributary they originated in for around 1,000 years.



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Life Sciences; Biology



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caddisfly, mtDNA, COI, SHM, PRH



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Biology Commons