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Abstract Although savanna woody encroachment has become a global phenomenon, relatively little is known about its effects on multiple dimensions and levels of savanna biodiversity.Using a combination of field surveys, a species‐level phylogeny, and functional metrics drawn from a morphological dataset, we evaluated how the progressive increase in tree cover in a fire‐suppressed savanna landscape affects the taxonomic, functional, and phylogenetic diversity of neotropical ant communities, at both the alpha and beta levels. Ants were sampled along an extensive tree cover gradient, ranging from open savannas to forests established in former savanna areas.Variation in tree cover had a significant influence on all facets of diversity at the beta level, whereas at the alpha level tree cover variation affected the taxonomic and functional but not the phylogenetic diversity of the ant communities.In general, ant community responses to variation in tree cover were largely non‐linear as differences in taxonomic alpha diversity and in the taxonomic, functional, and phylogenetic composition of the sampled communities were often much stronger at the savanna/forest transition than at any other part of the gradient. This indicates that savanna ant communities switch rapidly to an alternative state once the savanna turns into forest.Ant communities in the newly formed forest areas lacked many of the species typical of the savanna habitats, suggesting that the maintenance of a fire suppression policy is likely to result in a decrease in ant diversity and in the homogenisation of the ant fauna at the landscape scale.
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Morphological and Molecular Evidence Support Elevating Erythroxylum macrophyllum var. savannarum (Erythroxylaceae) to Specific Status
Erythroxylum macrophyllum is a morphologically variable and widely distributed species complex in Central and South America with several sub-specific taxa and numerous species included in its synonymy. A single variety grows in the Colombo-Venezuelan savanna region which can be distinguished from the rest of the E. macrophyllum complex by the size of leaves, cataphyll and stipule characteristics, and shape of calyx lobes. A molecular phylogeny reconstructed from 519 nuclear genes also reveals that the savanna variety is more closely related to E. acuminatum and E. pauciflorum than E. macrophyllum. This phylogenomic evidence also suggests Erythroxylum sect. Macrocalyx, to which E. macrophyllum belongs, is a polyphyletic taxonomic section. We thus propose elevating this variety to specific status, as Erythroxylum savannarum. We provide an updated taxonomic description, information about its habitat and distribution, and justify its informal IUCN cat- egorization of Near Threatened (NT)
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- Award ID(s):
- 2010821
- PAR ID:
- 10400004
- Date Published:
- Journal Name:
- Systematic botany
- Volume:
- 47
- Issue:
- 2
- ISSN:
- 0363-6445
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1600/036364422X16512572274990
