[Taxacom] Geographic structure in an ecologically weedy species

[John Grehan]

Heads (2014) wrote "The green tree skink Lamprolepis has a single, variable
‘species’, L. smaragdina, which is widespread from the Philippines and
Sulawesi to the Solomon Islands. It occurs iin mangrove and coastal
forests, and is also associated with human settlements, coconut plantations
and other disturbed habitats. It is rarely seen in dense, primary
rainforest.

In a detailed, well-sampled molecular study of Lamprolepis, Linkem et al
(2013) wrote that: “Widespread species found in disturbed habitats are
often expected to be human commensals. In island systems, this associate
predicts that dispersal will be mediated by humans.’ Nevertheless, Linkem
et al (2013) concluded that this does not apply to Lamprolepis as it
originated at 39 Ma and is composed of lineages with high levels of genetic
differentiation. In addition, the groups are highly structured in their
geography, with a jigsaw pattern of interlocking allopatry (Fig. 10.6).
these results repeat the unexpected discoveries of deep geographic
structure in the lizard Gehydra (Fig. 3.18) and other ‘weeds’ of
anthropogenic habitats. Groups capable of surviving in disturbed
environments such as mangrove and secondary forest often thrive in new
habitats such as gardens and plantations, but this does not mean they are
young groups. The authors wrote that the deep phylogenetic structure in
Lamprolepis is ‘contrary to expectations derived from its ecological
preference’ and it does contradict the traditional idea that weeds are
recent groups with random, unstructured distributions.

With respect to the dating of Lamprolepis, Linkem et al (2013) wrote that
the ages of various islands could provide ages of populations. They
regarded this as problematic, though, and instead relied on a rough
molecular rate for divergence dating. However, if the source of this rate
is traced back it leads to Gubitz et al (2000), who used the island ages in
the Canary islands to date an endemic gecko there. Thus the calculated date
of 39 Ma for the Lamprolepis/Lygosoma split is a minimum, island-calibrated
age.