Results
Of the 29,464 available COI barcode sequences, geographical
coordinates were available for 29,349 individuals (Figure 1). Excluding
identical syntopic haplotypes and individuals with incomplete
geographical coordinates, we retained for the analysis 16283 individuals
of 3967 species from 124 Coleoptera families. From these, we retained
only those species for which comprehensive ecological information was
available, such as feeding style, habitat and biotope preference, and
body size resulting in 12207 specimens available for final meta-analysis
representing 1785 species and 95 families of Coleoptera from Germany.
The majority of the species (above 400) was distributed in the distance
class “300”, the fewest species were in the class
“>300” (Figure S1). The number of species decreased
exponentially with the rising of the number of localities, with one
exception where only 190 species recorded 3 sampling localities (Figure
S1). Most species were zoophagous (n= 674) or phytophagous (n= 585),
while the preferred habitat was vegetation, which made up more than 600
species (n= 632) while dead wood and soil habitats accounted for 398 and
400 species, respectively (Figure S2). Across the preferred biotopes,
691 species preferred forest, many others either open-land (n= 420) or
wetland (n=369), and 305 had not specific preferences (Figure S2). The
most represented size-classes were, as expected, very small (n= 594) and
small (n= 626) species. The medium size class accounted for 386 species,
while the large and largest beetles counted 157 and 22 species,
respectively (Figure S2).
Infraspecific genetic distances resulted to be inversely proportional to
the number of sampled individuals and number of sampling localities
(Figure 3A-C), while intraspecific geographic distances were not
affected by sampling issues. Despite numerous cases with elevated
infraspecific divergence, distance plots across the four major
eco-classes of central European beetles (habitat, feeding preferences,
biotope, size class) revealed generally low intraspecific distances
(<3 % sequence divergence). Nevertheless, at first glance,
patterns of geographical and genetic differentiation differ clearly
among ecological and eco-morphological traits. Indeed, the plots (all
data) of geographical distance matrices versus genetic matrices showed
different shapes across different ecological guilds (Figure 3B-H, Figure
S3), particularly for habitat and feeding style. However, for the
biotope types no principal differences were visually evident (Figure
3G), although in biotopes, wetland and open land included more
long-distance samples than did forest and eurytopic biotopes. Body size
showed a clear trend that with the increase of body size (from
extra-small to extra-large) followed a mostly gradual decrease of the
infraspecific genetic distances (Figure 3F, Figure S3C). Larger
geographical distances occurred in saprophagous and phytophagous taxa or
species preferring wetland and vegetation, for which specimens had been
sequenced from outside of Germany (Figure S3). In saprophagous taxa, a
large amount of pairwise distances of specimens followed a nearly
proportional increase in both genetic and geographic distances. The same
was found for the xylophagous and zoophagous species. A different
pattern was evident in mycetophagous species where the genetic distances
were already much higher even with short geographic distances, while in
necrophagous, polyphagous and coprophagous species we observed the
opposite (with some minor exceptions), i.e., a clearly limited amount of
genetic variation even with increased geographic distance (Figure 3D).
In regard of habitat preferences, vegetation, rotten matters, and dead
woods had similar trends as taxa with phyto-, sapro-, and xylophagous
feeding style, obviously due to the connection between these
eco-classes. Species with habitats such as soil and nests had also a
higher genetic variation at same geographical scale, while others such
as the ”mushrooms/ fungi” inhabitants had comparatively lower genetic
structure despite a vast geographical sampling (Figure 3E).
All the three methods of correlation analysis between genetic and
geographical differentiation detected cases in which the expected
relationship between geographical and genetic distances were confirmed,
i.e., where all correlation approaches were positive (Figures S4, S5).
The Mantel test identified 250 species having a significant relationship
between the two distances (14% of the total number of examined
species), NMDS 160 species (9% of the total number of examined species)
and PCA 123 (6.8% of the total number of examined species). Overlap of
significant species between NMDS and Mantels test was 9.2%, while
species overlap of PCA with Mantel test was 9.6 % of and 32.5 % with
NMDS. This apparent discordance in identifying the significant species
with correlated patterns was evident from pairwise plots of significance
and statistic values of each species from the three methods (Figure S6):
while the PCA and NMDS methods agreed in both significance and statistic
values in most of the cases, both methods highly diverged with the
mantel resulting scores. Furthermore, maximum and minimal values of
significant species differed between the three methods (Tab. 1).
Significance for the ecological traits and their sub-guilds was rather
rare in all three approaches of correlation analysis (Figure S5).
Significance levels were too low to further use the outcome for further
trait investigation: these were in mean for all ecological guilds 7.5,
9.4, or 15.6 % for PCNM+PCA, NMDS+PCA, and Mantel test, respectively,
or at best 28% for a single guilt (Tab. 2). Some beetle families
entirely did not show significance (Figure S7). All three correlation
tests found coprophagous species to have the significantly more species
with significant correlation between genetic and geographic distances
(Tabs 1, 2). While the mantel test identified nest dwellers with the
lowest percentage the opposite was the case for NMDS and PCNM where the
nest dweller guild was the most dominant in significance. PCA and NMDS
recorded high percentages in significant species in nest habitat and
body size (i.e., extra-large), while small species were those dominant
for the Mantel test.