Data from: Ecological speciation by temporal isolation in a population of the stonefly Leuctra hippopus (Plecoptera, Leuctridae)

Stream dwelling invertebrates are ideal candidates for the study of
ecological speciation as they are often adapted to particular
environmental conditions within a stream and inhabit only certain reaches
of a drainage basin, separated by unsuitable habitat. We studied an
atypical population of the stonefly Leuctra hippopus at a site in central
Norway, the Isterfoss rapids, in relation to three nearby and two remote
conspecific populations. Adults of this population emerge about a month
earlier than those of nearby populations, live on large boulders emerging
from the rapids, and are short-lived. This population also has distinct
morphological features and was studied earlier during the period
1975–1990. We reassessed morphological distinctness with new measurements
and added several analyses of genetic distinctness based on mitochondrial
and nuclear sequence markers, as well as AFLP fingerprinting and SNPs
mined from RAD sequences. The Isterfoss population is shown to be most
closely related to its geographical neighbors, yet clearly morphologically
and genetically distinct and homogeneous. We conclude that this population
is in the process of sympatric speciation, with temporal isolation being
the most important direct barrier to gene flow. The shift in reproductive
season results from the particular temperature and water level regime in
the Isterfoss rapids. The distinct adult body shape and loss of flight are
hypothesized to be an adaptation to the unusual habitat. Ecological
diversification on small spatial and temporal scales is one of the likely
causes of the high diversity of aquatic insects.