3.2 Biogeography
The following biogeographical analyses were based on the MOTUs (370)
delimited by the sGMYC approach (see discussion below). In our dataset,
the number of species per sampling location varied from a single species
to over 15 species across the different sampling sites at the studied
biogeographical realms. Just a few of all sampled locations (3.8%) had
5 or more species present, while 203 (54.9%) of the 370 species
included were only recorded at a single location. Since collecting
methods, sampling sites, protocols and reporting varied in our dataset,
comparisons of overall biodiversity between locations is challenging.
Numbers of Polypedilum species and sampled locations varied
between regions (Table 1). Our results indicate that 90.2 % of species
were recorded only in a single major biogeographical region, while only
36 species spanned two or more of these regions.
The relative diversity and dominance of Polypedilum species as a
proportion of the total number of species per region shows a clear
divergence between the geographical regions studied (Figure 5).
Insufficiently sampled areas (Afrotropical, Australasian and Panamanian)
with low numbers of recorded species present low levels of diversity and
are dominated by few species. On the other hand, biogeographical regions
exhaustively sampled exhibit high numbers of recorded species with the
highest degree of species richness (Nearctic, Palearctic, Oriental and
Sino-Japanese). Regarding the Neotropics, the region presented moderate
levels of Polypedilum species diversity, particularly when
compared to the neighboring Nearctic region (Figure 5); however, it is
noteworthy that although only 6.2% of the sampling sites are located in
the Neotropical region (mostly in South America), 19.1% of the total
number of species occurred in this region. Moreover, based on our
results, the Neotropical Polypedilum fauna can be considered
endemic, since only one unidentified species was also recorded in the
Nearctic region.
None of the species accumulation (rarefaction) curves for the
biogeographical realms (Figure 6) exhibit asymptote for any area,
although the Nearctic sequences may be approaching one. The
Afrotropical, Australasian and Panamanian regions presented the lowest
levels of diversity. The highest levels of diversity were seen in the
Nearctic, Palearctic and Sino-Japanese regions, with the Neotropical and
Oriental regions curves being noticeably lower, with levels of diversity
which seems to be comparable. Biogeographical realm patterns across the
entire assembly (Figure 7a) showed distinct groupings for Afrotropical
and Australasian, while the ANOSIM (see Appendix S1) and nMDS results
show some overlap between Nearctic and Palearctic regions. The
Neotropical Polypedilum fauna despite the closeness to the
Nearctic region presents distinct clustering. The different Neotropical
zones compose distinct well supported groups (Figure 7b), with some
degree of overlap between Southeastern Amazonia and Boreal Brazilian
domination zones. In particular, the Palearctic region appears to
display affinities for both the Nearctic and Oriental region (Figure
7b).