In the last two centuries, the development of human civilization has transformed large natural areas into anthropogenic landscapes, making habitat fragmentation a pervasive feature of modern landscapes. In animal populations, habitat fragmentation may alter their genetic diversity and structure due to limited gene flow and dispersion and reduced effective population sizes, potentially leading to genetic drift in small habitat patches. We tested the hypothesis that habitat fragmentation affects genetic diversity of tetrapod populations through a meta‐analysis. We also examined certain life history traits of species and particular external landscape factors that may determine the magnitude of genetic erosion observed in fragmented habitats. Our results showed that habitat fragmentation reduces overall genetic diversity of tetrapod populations. Stronger negative fragmentation effects were detected for amphibians, birds and mammals. Within each taxonomic group, species with large body size were more strongly affected by fragmentation. Particularly within mammals, we found that less vagile species with short generation times represent the most susceptible tetrapod group to lose genetic diversity in fragmented habitats. As external drivers, we found a nonsignificant trend of lower fragmentation effects in study systems of less than 50 years and stronger effects in older (>100 years) fragmented systems. As expected, the extent of habitat loss was also important in determining the magnitude of genetic erosion in tetrapods. Extreme habitat loss showed stronger negative effects on genetic diversity irrespective of taxonomic groups. The information gathered in this review also highlights research bias and gaps in the literature.

No abstract

The Military Macaw (Ara militaris) is a globally threatened species with a fragmented distribution, and assessing the genetics of populations could help identify conservation units. Nine microsatellites were used to analyze 86 samples in seven localities along the Sierra Madre Occidental, the Sierra Madre del Sur, and the Sierra Madre Oriental in Mexico. Results showed that the Military Macaw has moderate levels of genetic diversity, similar to that found in other macaw species in Latin America. This species shows a high genetic structure; we find a genetic break between localities separated by the Central Plateau and the Trans-Mexican Volcanic Belt, which serve as geographic barriers. However, the locations within each genetic group are not genetically differentiated. It was observed that three locations of the Military Macaw have excess homozygotes, which could indicate a small effective size of the population and in combination with genetic isolation could increase the risk of extinction of the species. We propose two genetic groups for the species, the first comprising localities in the Sierra Madre Occidental and the Sierra Madre del Sur, and the second comprising localities of the Sierra Madre Oriental. According to the genetic differentiation, which was significant between the physiographic regions, and the unique allelic richness shown in this study, these two groups should be considered as independent conservation units. We strongly recommend the conservation and restoration of the natural habitats of the Military Macaw to maintain and increase the size of its population and recover and expand its original geographical distribution.

No abstract

No abstract