Coexistence: Causes And Differences Between Allopatric, And Bumblebees

Coexistence is the state in which two or more things exist together usually temporarily and with or without mutual relationship. A wide range of animals practise coexistence either between allopatric or sympatric organisms, these organisms includes Bees, Lizards, Birds, Ants etc which could be either through character displacement or resource partitioning . Character displacement is the phenomenon where differences among similar species whose distributions overlap geographically are accentuated in regions where the species co-occur, but are minimized or lost where the species distributions do not overlap while Resource partitioning is the process whereby same species exploit resources in the limited form in an ecological area without one species
Early studies on coexistence of bumblebees indicate that differences in the proboscis lengths of the species lead to resource partitioning by utilizing floral in different ways (Heinrich 1976, Ranta and Lundberg., 1980). Long-tongued bumblebee species (e.g. Bombus pascuorum) usually feed and exploit flowers with long corollas, whereas short-tongued species (e.g. Bombus terrestris agg., Bombus lapidarius, and Bombus pratorum) prefer more open shallow flowers (Brian., 1957, Teräs., 1985, Dramstad and Fry., 1995, Meek et al., 2002). It is important to note that proboscis length alone cannot completely explain coexistence in bumblebee communities, because locally co-occurring species differ only slightly in proboscis lengths (Ranta., 1982). Therefore, additional features or techniques may enable species coexistence in bumblebee communities (Pekkarinen., 1984), a typical example is the use of nesting sites (subterranean versus ground nesting species) which is a form of a additional technique (Kells and Goulson., 2003),and life cycles alteration due to imbalance in their phenology (early- versus late-season species) (Pekkarinen.,
Furthermore, the foraging ranges of bumblebees seem to be species specific (Walther-Hellwig and Frankl., 2000; Darvill et al., 2004). However, sound estimates of the specific foraging distances are difficult to obtain. Most studies are limited in sample size at large spatial scales, as the area in which a bee might forage increases with the square of the foraging distance (Walther-Hellwig and Frankl., 2000, Darvill et al., 2004), and homing experiments probably do not reveal the actual foraging ranges (Hedtke., 1994, Goulson and Stout., 2001). Potential foraging ranges seem to correspond with ecological traits of the bumblebee species. The large species B. terrestris and B. lapidarius are assumed to forage over long distances (Walther-Hellwig and Frankl., 2000), and they establish colonies with numerous workers (von Hagen., 1994). The smaller B. pascuorum and B. pratorum presumably have small foraging ranges (Mauss and Schindler., 2002), and they establish smaller colonies (von Hagen., 1994). It is suggested that not only food plant or patch preferences, but also different patterns of spatial resource utilisation might favour coexistence in bumblebee communities, if the foraging ranges of bumblebees are in fact species-specific. An important prerequisite for the