1 Citation 286 Views 45 Downloads
The fossil record provides an important source of data on adaptive
radiations, and indeed some of the earliest theoretical insights on the
nature of these radiations were made by paleontologists. Here we focus on
the diverse Devonian Metacryphaeus group calmoniid trilobites, known from
the Malvinokaffric Realm; these have been considered a classic example of
an adaptive radiation preserved in the fossil record. A geometric
morphometric analysis is used in conjunction with phylogenetic and
biogeographic patterns and data on speciation rates. Patterns of
morphological change are quantified using ancestral character state
reconstruction during speciation events in order to assess the role
ecological and geographical factors may have played in mediating this
radiation. No significant differences were found between the amount of
morphological change that occurred during speciation events when ancestors
and descendents were in the same area as opposed to when they occupied
different areas. Further, the magnitude of morphological divergence did
not change through time or with cladogenetic rank. These patterns, in
conjunction with the fact that the radiation occurs in a geographically
heterogeneous region subjected to repeated episodes of sea-level rise and
fall, suggests that at the macroevolutionary scale this radiation may have
been motivated more by phenomena that facilitated geographic isolation
than by competition.
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