Separated cases of static allometry reflect structural changes in the
macroevolution of the male genitalia in Limnebius beetles
Abstract
Limnebius water beetles exhibit exceptionally high diversification of
male genitalia but a uniform external appearance. We examined a
connection between the magnitude of interspecific variability in each
subgroup and static allometry between male genitalia and body size.
Several lineages with simple genitalia show low diversification of body
and male genitalia. High magnitude is caused by diversification among
lineages with different complexity compositions of male genitalia and
clusters of species with small and large body sizes. In the Limnebius
parvulus group high intraspecific variability corresponds between the
coefficients of static allometry, size of male genitalia, variabilities
of female body size, indicating a role of the females in the selection
of wide and long male genitalia. The general evolutionary trend of the
genera fits with the superposition of all intraspecific allometries. It
is usually neutral; negative is associated with local picks of the male
genitalia complexity, featuring a trade-off between size and complexity,
reflected in the magnitude of the corresponding values, Positive was
observed only on the populational level, with negative allometry in the
same species in a rapidly evolving species complex in the L. nitidus
group. The L. nitidus subgroup exposes the highest magnitude of the male
genitalia complexity and the ventral area, evolving faster than length.
Intraspecific heterogeneity is also featured by two specimens with long
genitalia in species from the same subgroup, with the simplest male
genitalia in its subgenera. The phylogenetic position of both
heterogeneous species featuring abrupt changes in male genitalia
illustrates macroevolution on a microevolutionary level.