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- Meyer-Lucht, Yvonne, et al.
(författare)
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Selection, diversity and evolutionary patterns of the MHC class II DAB in free-ranging Neotropical marsupials
- 2008
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Ingår i: BMC Genetics. - : Springer Science and Business Media LLC. - 1471-2156. ; 9, s. 39-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Research on the genetic architecture and diversity of the MHC has focused mainly on eutherian mammals, birds and fish. So far, studies on model marsupials used in laboratory investigations indicated very little or even no variation in MHC class II genes. However, natural levels of diversity and selection are unknown in marsupials as studies on wild populations are virtually absent. We used two endemic South American mouse opossums, Gracilinanus microtarsus and Marmosops incanus, to investigate characteristic features of MHC selection. This study is the first investigation of MHC selection in free-ranging Neotropical marsupials. In addition, the evolutionary history of MHC lineages within the group of marsupials was examined.Results: G. microtarsus showed extensive levels of MHC diversity within and among individuals as 47 MHC-DAB alleles and high levels of sequence divergence were detected at a minimum of four loci. Positively selected codon sites were identified, of which most were congruent with human antigen binding sites. The diversity in M. incanus was rather low with only eight observed alleles at presumably two loci. However, these alleles also revealed high sequence divergence. Again, positive selection was identified on specific codon sites, all congruent with human ABS and with positively selected sites observed in G. microtarsus. In a phylogenetic comparison alleles of M. incanus interspersed widely within alleles of G. microtarsus with four alleles being present in both species.Conclusion: Our investigations revealed extensive MHC class II polymorphism in a natural marsupial population, contrary to previous assumptions. Furthermore, our study confirms for the first time in marsupials the presence of three characteristic features common at MHC loci of eutherian mammals, birds and fish: large allelic sequence divergence, positive selection on specific sites and trans-specific polymorphism.
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| 2. |
- Meyer-Lucht, Yvonne, et al.
(författare)
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Variety matters : adaptive genetic diversity and parasite load in two mouse opossums from the Brazilian Atlantic forest
- 2010
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Ingår i: Conservation Genetics. - : Springer Science and Business Media LLC. - 1566-0621 .- 1572-9737. ; 11:5, s. 2001-2013
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Tidskriftsartikel (refereegranskat)abstract
- The adaptive potential of a species to a changing environment and in disease defence is primarily based on genetic variation. Immune genes, such as genes of the major histocompatibility complex (MHC), may thereby be of particular importance. In marsupials, however, there is very little knowledge about natural levels and functional importance of MHC polymorphism, despite their key role in the mammalian evolution. In a previous study, we discovered remarkable differences in the MHC class II diversity between two species of mouse opossums (Gracilinanus microtarsus, Marmosops incanus) from the Brazilian Atlantic forest, which is one of the most endangered hotspots for biodiversity conservation. Since the main forces in generating MHC diversity are assumed to be pathogens, we investigated in this study gastrointestinal parasite burden and functional associations between the individual MHC constitution and parasite load. We tested two contrasting scenarios, which might explain differences in MHC diversity between species. We predicted that a species with low MHC diversity would either be under relaxed selection pressure by low parasite diversity ('Evolutionary equilibrium' scenario), or there was a recent loss in MHC diversity leading to a lack of resistance alleles and increased parasite burden ('Unbalanced situation' scenario). In both species it became apparent that the MHC class II is functionally important in defence against gastrointestinal helminths, which was shown here for the first time in marsupials. On the population level, parasite diversity did not markedly differ between the two host species. However, we did observe considerable differences in the individual parasite load (parasite prevalence and infection intensity): while M. incanus revealed low MHC DAB diversity and high parasite load, G. microtarsus showed a tenfold higher population wide MHC DAB diversity and lower parasite burden. These results support the second scenario of an unbalanced situation.
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| 3. |
- Puettker, Thomas, et al.
(författare)
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Effects of fragmentation on parasite burden (nematodes) of generalist and specialist small mammal species in secondary forest fragments of the coastal Atlantic Forest, Brazil
- 2008
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Ingår i: Ecological research. - : Wiley. - 0912-3814 .- 1440-1703. ; 23:1, s. 207-215
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Tidskriftsartikel (refereegranskat)abstract
- Parasites are considered to play an important role in the regulation of wild animal populations. We investigated parasite burden of gastrointestinal nematodes and body condition in specialist and generalist small mammal species in secondary forest fragments in the highly endangered coastal Atlantic Forest. We hypothesized that body condition decreases with increasing parasite load and that parasite burden increases with increasing fragmentation in specialist species but not in generalist species as a consequence of differing responses to fragmentation effects. Investigated species were Akodon montensis, Oligoryzomys nigripes, and Delomys sublineatus (rodents) and the marsupials Marmosops incanus and Gracilinanus microtarsus. Prevalence of parasites was high in all species except for the arboreal G. microtarsus, presumably because of decreased infection probability. No correlation was found between body condition and parasite load in any of the species. Contrary to our expectations, body condition of the specialists D. sublineatus and M. incanus increased in both species with increasing fragmentation. In D. sublineatus, parasite burden increased and body condition decreased in fragments with relatively high density probably due to increased contact rates and facilitation of infection with nematodes. In all generalist species, low or no correlation between parasite burden and fragmentation was detected, suggesting little effect of fragmentation on population health.
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| 4. |
- Puettker, Thomas, et al.
(författare)
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Fragmentation effects on population density of three rodent species in secondary Atlantic Rainforest, Brazil
- 2008
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Ingår i: Studies on Neotropical Fauna and Environment. - : Informa UK Limited. - 0165-0521 .- 1744-5140. ; 43:1, s. 11-18
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the population density of the two common rodent species Akodon montensis, Oligoryzomys nigripes, and the more specialized endemic Delomys sublineatus in secondary forest fragments of the highly endangered coastal Atlantic Rainforest. Linear regression was used to examine relationships between population density and four landscape variables. We tested the hypothesis that rare species, which are more affected by fragmentation than the common species, should decrease in population density with decreasing fragment size while the density of common generalist species should be unaffected or increase in smaller fragments. The results revealed that A. montensis and O. nigripes showed no significant association to any landscape variable. The density of D. sublineatus showed a strong tendency to a positive correlation to fragment size as well as a negative correlation to edge density. The results underline the importance of large and connected forest remnants in the Atlantic Rainforest to guarantee an effective protection of endemic small mammal species.
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| 5. |
- Puettker, Thomas, et al.
(författare)
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Movement distances of five rodent and two marsupial species in forest fragments of the coastal Atlantic rainforest, Brazil
- 2006
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Ingår i: Ecotropica (Bonn). - 0949-3026. ; 12:2, s. 131-139
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Tidskriftsartikel (refereegranskat)abstract
- Movement distances provide information on diverse Population biological parameters and are essential in understanding the ecology of a species. Mean distances moved between successive captures (SD), distribution of movement distances, and the mean maximum distances moved (MMDM) were investigated in five rodent and two marsupial species in forest fragments of the coastal Atlantic rainforest (Mata Atlantic) in the state of Sao Paulo, Brazil. The investigated species were the rodents Akodon montensis (Thomas, 1902), Oligoryzomys nigripes (Olfers, 1818), Delomys sublineatus (Thomas, 1903), Oryzomys russatus (Wagner, 1848), and Thaptomys nigrita (Lichtenstem, 1829), and the marsupials Mannosops incanus (Lund 1840), and Cracilinanus microtarsus (Wagner, 1842). Akodon montensis differed significantly from all other species and moved the lowest SD and MMDM. The marsupials differed significantly from most of the rodents and moved the largest SDs. All species showed the highest Frequency of movements in a distance class of 0-20 m. Differences between sexes in SD was detected for O. nivipes, O. russatus, and C. microtarsus, males moving significantly longer distances than females. The different Study sites had no influence on SD in any of the investigated species. Only the males of G. microtarsus showed a seasonal variation in SD, moving longer distances during reproductive activity. Accepted 15 August 2006.
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| 6. |
- Puettker, Thomas, et al.
(författare)
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Responses of five small mammal species to micro-scale variations in vegetation structure in secondary Atlantic Forest remnants, Brazil
- 2008
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Ingår i: BMC Ecology. - : Springer Science and Business Media LLC. - 1472-6785. ; 8, s. 9-Article No.: 9
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Tidskriftsartikel (refereegranskat)abstract
- Background: The Brazilian Atlantic Forest is highly endangered and only about 7% of the original forest remains, most of which consists of fragments of secondary forest. Small mammals in the Atlantic Forest have differential responses to this process of fragmentation and conversion of forest into anthropogenic habitats, and have varying abilities to occupy the surrounding altered habitats. We investigated the influence of vegetation structure on the micro-scale distribution of five small mammal species in six secondary forest remnants in a landscape of fragmented Atlantic Forest. We tested whether the occurrence of small mammal species is influenced by vegetation structure, aiming to ascertain whether species with different degrees of vulnerability to forest fragmentation (not vulnerable: A. montensis, O. nigripes and G. microtarsus; vulnerable: M. incanus and D. sublineatus; classification of vulnerability was based on the results of previous studies) are associated with distinct vegetation characteristics.Results: Although vegetation structure differed among fragments, micro-scale distribution of most of the species was influenced by vegetation structure in a similar way in different fragments. Among the three species that were previously shown not to be vulnerable to forest fragmentation, A. montensis and G. microtarsus were present at locations with an open canopy and the occurrence of O. nigripes was associated to a low canopy and a dense understory. On the other hand, from the two species that were shown to be vulnerable to fragmentation, M. incanus was captured most often at locations with a closed canopy while the distribution of D. sublineatus was not clearly influenced by micro-scale variation in vegetation structure.Conclusion: Results indicate the importance of micro-scale variation in vegetation structure for the distribution of small mammal species in secondary forest fragments. Species that are not vulnerable to fragmentation occurred at locations with vegetation characteristics of more disturbed forest, while one of the species vulnerable to fragmentation was found at locations with older forest characteristics. Results suggest that micro-habitat preferences may be an important factor influencing the capacity of small mammals to occupy altered habitats and, consequently, their vulnerability to forest fragmentation at a larger spatial scale.
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