Different mechanisms underlie similar species-area relationships in two tropical archipelagoes

Despite much research in the field of island biogeography,mechanisms regulating insular diversity remain elusive.Here,we aim to explore mechanisms underlying plant species-area relationships in two tropical archipelagoes in the South China Sea.We found positive plant species-area relationships for both coral and continental archipelagoes.However,our results showed that different mechanisms contributed to similar plant species-area relationships between the two archipelagoes.For coral islands,soil nutrients and spatial distance among communities played major roles in shaping plant community structure and species diversity.By contrast,the direct effect of island area,and to a lesser extent,soil nutrients determined plant species richness on continental islands.Intriguingly,increasing soil nutrients availability(N,P,K)had opposite effects on plant diversity between the two archipelagoes.In summary,the habitat quality effect and dispersal limitation are important for regulating plant diversity on coral islands,whereas the passive sampling effect,and to a lesser extent,the habitat quality effect are important for regulating plant diversity on continental islands.More generally,our findings indicate that island plant species-area relationships are outcomes of the interplay of both niche and neutral processes,but the driving mechanisms behind these relationships depends on the type of islands.

Brachyuran Crab Fauna Character Estimated from Marine Water of Bangladesh and Noted New Record (Crustacea: Decapoda) as Distribution

As habitat and distribution, in the study a total of 18 crab species were identified, belonging to 10 families (Calappidae, Epialtidae, Gecarcinidae, Grapsidae, Matutidae, Ocypodidae, Panopeidae, Sesarmidae, Varunidae, and Xanthidae) order Decapoda under subphylum crustacean with relevant distinguish morphological and meristic character and geographical position. We investigated crab species of Bangladesh from December 2013 to October 2014. All species samples were collected by hand picking on a baseline survey in Saint Martin’s Island (the only coral island of Bangladesh) and adjacent marine water body of Bay of Bengal, Satkhira area (brackish and freshwater) and mangrove forest area (Sundarban). Among 18 species, 10 crab species from Family Epialtidae (1 species), Gecarcinidae (2 species), Ocypodidae (1 species), Panopeidae (1 species), Sesarmidae (1 species) and Xanthidae (4 species) were newly occurred in the Bay of Bengal, Bangladesh. Cardisoma armatum and Zosymus aeneus species were larger than other enlisted species.