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Habitat loss has major impacts on biodiversity. Yet, such impacts are not always linear, as there can be threshold values of habitat amount below which species become extirpated from human-modified landscapes (extinction thresholds). This may be particularly the case for species with high habitat spatial requirements, especially in regions with a long land-use history, which have a lower extinction debt. To address these issues, we evaluated the linear and non-linear effects of landscape-scale forest (habitat) loss on primate species richness in regions with relatively new (Amazon) and old (Atlantic Forest) histories of land-use change. We also evaluated the role of mean home range size in regulating species responses to forest loss. Extinction thresholds were higher in the Atlantic Forest (78% remaining forest cover) than in the Amazon (45%), but primate-landscape associations were stronger in the Amazon. Thus, despite its recent land-use history, Amazon primates are more sensitive to habitat loss. As predicted, mean home range size decreased with forest loss in both biomes. Our findings highlight the importance of stopping deforestation in both biomes to maintain habitat amount above these thresholds. Yet, as

Lake Naivasha is a shallow, freshwater lake in the eastern Rift Valley of Kenya. Its fish community now comprises only introduced species. Oreochromis spirulus niger was stocked in 1925 as a forage fish for the largemouth bass, Micropterus salmoides, introduced in 1929 for sport fishing. Further introductions of tilapiines followed for commercial exploitation. A gillnet fishery opened in 1959, and the annual species catch composition to 2000 was dominated by Oreochromis leucostictus. Following their accidental introduction, carp Cyprinus carpio appeared in catches in 2002; by 2010, it comprised >99% of landings by weight. Carp now provides a sustainable fishery in a lake heavily impacted by anthropogenic stressors, including water abstraction and nutrient enrichment. Oreochromis niloticus was reintroduced in 2011 to reinvigorate tilapia stocks following the collapse of its stocks in the 1990s and early 2000s, and the African catfish Clarias gariepinus is now captured in small but increasing numbers. The current status of the fishery, especially the predominance of carp, presents major management challenges; these are addressed by stakeholder engagement and co-management. The introductions have artificially created a commercial fishery that provides substantial societal benefits in a semi-arid region of a developing country with high poverty levels. [ABSTRACT FROM AUTHOR]

Among the major changes induced by human beings, biotic homogenization is gaining popularity at regional as well as global level. Biotic homogenization is a multifaceted process which results from species extinction, introduction and environmental modification often induced by human beings. This human mediated introduction of alien species and the extirpation of native species, either independently or in combine have caused loss of taxonomic regional distinctiveness among formerly disparate faunas and floras. Ample evidence reveals that extent of homogenization differed between various ecosystems and taxa, as well as in different regions. Although biotic homogenization leads to increase in species richness at local level but causes loss of diversity at global level (i.e., paradox of gaining species but loosing diversity). Potentially biotic homogenization could affect any of the many processes in communities that vary in space and time, such as spatial subsidies and food-web dynamics, and thereby have cascading effects elsewhere on the landscape. Biotic homogenization does have relevance to conservation as it has utility in reserve selection and management. Current knowledge pertaining to patterns, mechanisms and implications of biotic homogenization is highly variable across taxonomic groups, but in general is incomplete. This article is an attempt to review literature pertaining to patterns, mechanisms and implications of biotic homogenization. [ABSTRACT FROM AUTHOR]

Ecological niche models provide useful predictions of species distributions, but may fail to detect reductions in distribution due to factors other than habitat loss, such as hunting or trade. From 2001 to 2009, we conducted field-surveys along the Mexican Pacific coast to obtain presence-absence data for nine Psittacidae species. We applied Genetic Algorithm for Rule set Prediction (GARP) ecological niche modeling, using field-survey presence data to determine the potential current distribution of each species, and incorporated absence data to delineate extirpation areas. All parrot species showed a reduced current distribution, ranging from 9.6 to 79% reduction of estimated original distribution. The threatened and endemic species of Amazona oratrix, Amazona finschi, and Forpus cyanopygius suffered the greatest distribution reduction, higher than previously estimated by habitat-based models, suggesting that capture for trade may have caused extirpation of these species. The greatest extent of current distribution was occupied by Aratinga canicularis, Amazona albifrons and Ara militaris, which continue to occur throughout most of their original distribution. Amazona auropalliata, Aratinga strenua, and Brotogeris jugularis also occur throughout their restricted distribution in coastal Chiapas, and show a relatively small distribution reduction, but had the highest proportion of modified lands within their current distributions. Our results highlighted the regions of coastal Guerrero, northern Nayarit, and southern Sinaloa where parrot species have been extirpated even though GARP models predicted suitable habitat available. Ideally distribution models should be verified in the field to determine conservation priorities, and efforts should be directed to maintain populations of species with greatest distribution reductions. [ABSTRACT FROM AUTHOR]

River floodplain ecosystems host one of the highest freshwater molluscan biodiversity on Earth. However, multiple human disturbances, such as loss of hydrological connectivity and deterioration of water quality, are seriously threatening most floodplain lakes throughout the world. Given the high imperilment rate of freshwater molluscs but the scarcity of studies examining the anthropogenic effects on this fauna, we test the response of mollusc assemblages to river-lake disconnection and eutrophication in 30 lakes in the Yangtze River floodplain, China. The species richness of entire Mollusca, Gastropoda and Bivalvia and 6 dominant families were all much lower at disconnected lakes than that in connected lakes, and decreased with increasing water eutrophication. The assemblage structure differed significantly among four lake groups for datasets based on entire Mollusca, Gastropoda and Bivalvia, indicating the serious impacts of hydrological disconnection and eutrophication. Moreover, the connected lakes showed significantly lower values of average taxonomic distinctness (Δ+) but higher values of variation in taxonomic distinctness (Λ+) than disconnected lakes. Such variations were triggered by the extirpation of congeneric and endemic species (mainly from families Unionidae and Viviparidae), which giving a waring of the loss of mollusc endemism in this region. In general, the present study showed that river-lake disconnection and deterioration of water quality resulted in serious biodiversity declines of both gastropods and bivalves in the Yangtze River floodplain lakes. A systematic approach including restoration of river-lake connectivity and habitats and improvement of water quality should be implemented in the conservation planning in this large river floodplain. • We test how floodplain disconnection and eutrophication affected molluscs in 30 lakes. • The disturbances caused serious decline of species in both Gastropoda and Bivalvia. • Mollusc assemblages structure differed significantly among four lake groups. • Such variations were triggered by the extirpation of congeneric and endemic molluscan species. [ABSTRACT FROM AUTHOR]