Early burst in body size evolution is uncoupled from species diversification in diving beetles (Dytiscidae)

• Changes in morphology are often thought to be linked to changes in species diversification,which is expected to leave a signal of early burst (EB) in phenotypic traits.However, such signal is rarely recovered in empirical phylogenies, even for groupswith well-known adaptive radiation. Using a comprehensive phylogenetic approachin Dytiscidae, which harbours ~4,300 species with as much as 50-fold variation inbody size among them, we ask whether pattern of species diversification correlateswith morphological evolution. Additionally, we test whether the large variation inbody size is linked to habitat preference and whether the latter influences speciesturnover. We found, in sharp contrast to most animal groups, that Dytiscidae bodysize evolution follows an early-burst model with subsequent high phylogenetic conservatism.However, we found no evidence for associated shifts in species diversification,which point to an uncoupled evolution of morphology and speciesdiversification. We recovered the ancestral habitat of Dytiscidae as lentic (standingwater), with many transitions to lotic habitat (running water) that are concomitantto a decrease in body size. Finally, we found no evidence for difference in net diversificationrates between habitats nor difference in turnover in lentic and lotic species.This result, together with recent findings in dragonflies, contrasts with sometheoretical expectations of the habitat stability hypothesis. Thus, a thoroughreassessment of the impact of dispersal, gene flow and range size on the speciationprocess is needed to fully encompass the evolutionary consequences of the lentic–lotic divide for freshwater fauna.

Ämnesord

NATURVETENSKAP  -- Biologi -- Biologisk systematik (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biological Systematics (hsv//eng)

NATURVETENSKAP  -- Biologi -- Evolutionsbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Evolutionary Biology (hsv//eng)

NATURVETENSKAP  -- Biologi -- Zoologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Zoology (hsv//eng)

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

Nyckelord

body size

divergence time

early burst

habitat

insect

phylogeny

Diversity of life

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