Page 39 - Lo Cascio_2015

Worldwide checklist of the island mutillid wasps (Hymenoptera Mutillidae) 567

predatory wasps belonging to 31 families, many of species (356), some of which are also distributed
which are brachypterous or even apterous (Jennings in the neighboring regions (7 shared with Aus-
& Austin, 2015), but curiously not by Mutillidae, tralasia, 7 with E Palearctic, and 1 with this latter
although the island could have both suitable hab- and Oceania). Mutillidae are generally character-
itats and hosts. ized by a greater diversity in the tropical and sub-
Is therefore to believe that isolation is not just a tropical regions of the world (Lelej & Brothers,
question of distance, but related to the nature of 2008), while in the northern areas their number
wind system, as observed for the Antillean butter- strongly decrease, and this pattern seems to be con-
flies by Spencer-Smith et al. (1988), or of course firmed also on islands when comparing Nearctic to
even stochastic. Neotropic, or W-Palearctic to Afrotropical. It
An intriguing example for understanding time should be noted that two of the three species oc-
and space scales of the island colonization is given curring in Great Britain have been included among
by that of the volcanic micro-archipelago of the “notable” at national level due to their relative
Krakatau (Indonesia) after the devastating eruption rarity (Falk, 1991). However, the noteworthy
occurred in 1883. Forty years later, Dammermann species richness of Indo-Malay may be explained
(1923) recorded the occurrence of females belong- also by the fact that this region includes the islands
ing to two unidentified species (only one on characterized by the highest number of species (Sri
Sertung, both on Rakata Besar) not found during Lanka and Borneo, respectively with 82 and 77),
previous surveys (see Jacobson, 1909), and once as well as countries where occur a large number of
again Dammermann (1948) reported two and three islands (Indonesia and Philippines).
unidentified species, respectively, for these islands. A highly significant correlation between island
O’Toole (1975) remarked that at least one of them, size and number of species (log species - log area : r =
Wallacidia melmora (Cameron, 1905), is able to 0.569, P = 0.0004) was found for N = 39 islands
2
overcome narrow sea barriers (about 50 Km) thanks with a surface >10,000 Km (excluding North
to the peculiar morphology of the genitalia that Island, where the only occurring species has been
ensures a prolonged female phoresy during the surely introduced; Great Britain, Ireland, Vancouver
mating, assuming however as the colonization of and Sakhalin,whose faunal impoverishment real-
new islands must necessarily occurred after the istically reflects a latitudinal constraint; and Marajó,
settling of its potential hosts. that according to the literature has not been ad-
Also passive dispersal (by human-mediated, equately investigated) (Fig. 2).
accidental introductions) may play a role in the oc- Likewise, highly significant correlations were
currence of mutillids wasps on insular environ- found for Mediterranean (excluding those not ad-
ments. The Australian “Ephutomorpha” bivulnerata equately investigated, N = 47: r = 0.830, P =
(André, 1901) not long ago recorded for North 0.0001) (Fig. 3), Japanese and Nansei (N = 21: r =
Island has been interpreted in this sense (Valentine 0.758, P = 0.0001) (Fig. 4), Indo-Malay (excluding
& Walker, 1983). Furthermore, two females and one Nansei, N = 49: r = 0.717, P = 0.0001), Australasian
male of Sphaeropthalma pensylvanica (Lepeletier, (excluding North Island, N = 54: r = 0.511, P =
1845) were recently found yet in New Zealand 0.0002; including Australia, N = 55: r = 0.640, P =
during the reclamation of used vehicles imported 0.0001), Caribbean (N = 19: r = 0.615, P = 0.004)
from United States (Toy, 2007); the latter record (Fig. 5), and Afrotropic islands (N = 15: r= 0.721,
was anyway not included in the present checklist P = 0.003) (Fig. 6).
because it concerns an unnatural context. Likewise, Highly significant linear correlations were also
Sugiura et al. (2013) considered Neotrogaspidia found between number of species and island eleva-
pustulata (Smith, 1873) an alien species in the tion, that may give an indirect indication of the
Ogasawara Islands. environmental heterogeneity of such territories, for
Mediterranean (r = 0.840, P = 0.0001), Indo-Malay
Species richness (r = 0.586, P = 0.0001), Japanese and Nansei (r =
0.850, P = 0.0001), Australasian (r = 0.614, P =
As shown in figure 1, the islands of the Indo- 0.0006), and Caribbean (excluding Trinidad, N =
Malay ecoregion host the highest number of 18: r = 0.695, P = 0.001).