Land use changes in an afrotropical biodiversity hotspot affect stream alpha and beta diversity

Fugère, Vincent; Kasangaki, Aventino; Chapman, Lauren J.

doi:10.1002/ecs2.1355

Cited by 44 publications

(52 citation statements)

References 82 publications

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“…In tropical agroecosystems, β‐diversity patterns based on different facets are largely unknown (Fugère et al., ; Karp et al., ). Furthermore, the effects of environmental disturbance on β‐diversity in streams are much more difficult to predict because there is scarce empirical evidence (Fugère et al., ). Our study has clear implications for the protection of regional fish diversity and should be integrated into stream management.…”

Section: Discussionmentioning

confidence: 99%

Taxonomic, functional, and phylogenetic β‐diversity patterns of stream fish assemblages in tropical agroecosystems

et al. 2019

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A multi‐faceted assessment of diversity is needed to improve our understanding of the mechanisms underlying biodiversity patterns and to reveal the impacts of land use alterations on β‐diversity. In this study, we analysed stream fish β‐diversity based on taxonomic, functional, and phylogenetic facets in an intensively cultivated tropical region. We sampled 43 stream reaches in the northwest of São Paulo State, south‐eastern Brazil. Each sampling site was characterised according to catchment‐scale features, landscape dynamic indicators, local‐scale features, and distance between stream reaches as network distance (a proxy for dispersal processes). As response variables, we considered taxonomic, functional, and phylogenetic β‐diversities coupled with a null‐model approach. For each β‐diversity metric, we calculated the mean overall value and tested whether the mean value was different from that expected by chance. To examine variation in β‐diversity for the three facets and determine the relative contributions of predictor variables, we used a distance‐based approach. Taxonomic and functional β‐diversities were higher from the expected value under a null model, suggesting that community assembly of these facets was dominated by deterministic processes. In contrast, phylogenetic β‐diversity was not different from that expected by chance, suggesting that the lineage composition of these assemblages was random. Furthermore, for all three facets, there was a positive environment‐β‐diversity relationship that was determined primarily by local‐scale features, whereas catchment features and landscape dynamic indicators were not important. In addition, none of the β‐diversity facets was correlated with stream network distance, indicating that dispersal processes were not strongly structuring fish assemblages. Our study suggested that although multiple facets of stream fish β‐diversity are ruled mainly by deterministic processes (e.g. species sorting), stochasticity is also important in community assembly. An interesting finding was the mismatch between phylogenetic versus taxonomic and functional β‐diversity. It is likely that the lack of non‐random structure in phylogenetic β‐diversity is due to the variation of phylogenetic signal in some functional traits. Given that landscape dynamic indicators were not correlated with measures of β‐diversity, we suggest that the recent sugarcane expansion in our study area probably has not critically affected stream fish β‐diversity. Also, it is possible that catchment variables presented little variability and did not overwhelm the effect of local environmental variables on β‐diversity. In conclusion, our study suggests that even highly disturbed tropical agroecosystems with a pool of species that is probably decimated, can still display a relatively high β‐diversity determined mainly by species sorting. These findings suggest key environmental features that must be considered in restoration or conservation of β‐diversity in agroecosystems. Specifically, since variation i...

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Section: Discussionmentioning

confidence: 99%

Taxonomic, functional, and phylogenetic β‐diversity patterns of stream fish assemblages in tropical agroecosystems

et al. 2019

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“…Given the extremely low alpha diversity and sparse species pool of these positive indicator species in the high‐stress group, increased beta diversity due to heterogeneous stress may actually be an early warning sign of environmental degradation that will diminish diversity if allowed to persist (de Juan, Thrush, & Hewitt, ). Even in scenarios where gamma diversity is maintained by high species turnover, problems may still arise if functionally important taxa are absent from disturbed sites (Fugère et al, ). For these reasons, changes in beta diversity, even positive ones, may be cause for concern in anthropogenically modified or stressed systems.…”

Section: Discussionmentioning

confidence: 99%

Beta diversity response to stress severity and heterogeneity in sensitive versus tolerant stream diatoms

Pound

Lawrence

Passy

2018

Diversity and Distributions

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Aim Severity and heterogeneity of stress are major constraints of beta diversity, but their relative influence is poorly understood. Here, we addressed this question by examining the patterns of beta diversity in stress‐sensitive versus stress‐tolerant stream diatoms and their response to local versus regional factors along gradients of stress severity and heterogeneity. Location The Adirondack region of New York. Methods Beta diversity was measured as multivariate dispersion of communities across high stress, low stress, and high + low stress (heterogeneous) environments, encompassing 200 stream samples. Null models were implemented to assess community similarity relative to randomly assembled communities and the importance of local assembly processes versus the regional species pool. Results The overall beta diversity was influenced by a combination of severity and heterogeneity of stress, while beta diversity of sensitive species increased with heterogeneity. Beta diversity of tolerant species did not vary with either severity or heterogeneity of stress. Heterogeneity decreased community similarity relative to the null expectation in all groups of species. Stress reduced the importance of local assembly mechanisms for the overall beta diversity and sensitive species beta diversity. In contrast, the importance of local assembly mechanisms increased with stress regarding beta diversity of tolerant species. Main conclusions Beta diversity responded to both severity and heterogeneity of stress, but turnover along these gradients was mostly driven by sensitive species. The overall beta diversity and beta diversity of sensitive species became more constrained by the depauperate regional species pool, as opposed to local assembly mechanisms. While heterogeneous stress contributed to beta diversity, severe stress suppressed beta diversity through elimination of sensitive species. Therefore, an increase in beta diversity in an environmentally‐stressed region may serve as a forewarning for future loss of sensitive species, should the stress continue to intensify.

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“…Doherty, Sitch, Smith, Lewis, & Thornton, ; Mittermeier, Turner, Larsen, Brooks, & Gascon, ; White, ). However, African forests and semiarid lands are already changing as a result of pressure from climate and land‐use change (Fugère, Kasangaki, & Chapman, ; Newmark & McNeally, ; Niang, Ruppel, & Abdrabo, ). In turn, feedbacks associated with altered disturbance regimes, such as wildfires, on landscapes processes could result in detrimental changes to important ecosystems services (e.g.…”

Section: Introductionmentioning

confidence: 99%

Waxing and waning of forests: Late Quaternary biogeography of southeast Africa

Ivory

Lézine

Vincens

et al. 2018

Global Change Biology

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African ecosystems are at great risk. Despite their ecological and economic importance, long-standing ideas about African forest ecology and biogeography, such as the timing of changes in forest extent and the importance of disturbance, have been unable to be tested due to a lack of sufficiently long records. Here, we present the longest continuous terrestrial record of late Quaternary vegetation from southern Africa collected to date from a drill core from Lake Malawi covering the last ~600,000 years. Pollen analysis permits us to investigate changes in vegetation structure and composition over multiple climatic transitions. We observe nine phases of forest expansion and collapse related to regional hydroclimate change. The development of desert, steppe and grassland vegetation during arid periods is likely dynamically linked to thresholds in regional hydrology associated with lake level and moisture recycling. Species composition of these dryland ecosystems varied greatly and is unlike the vegetation found at Malawi today, with assemblages suggesting strong Somali-Masai affinities. Furthermore, nearly all semiarid assemblages contain low forest taxa abundances, suggesting that moist lowland gallery forests formed refugia along waterways during arid times. When the region was wet, forests were species-rich and very high afromontane tree abundances suggest frequent widespread lowland colonization by modern high elevation trees. Furthermore, species composition varied little amongst forest phases until ~80 ka when disturbance tolerant tree taxa characteristic of the modern vegetation increased in abundance. The waxing and waning of forests has important implications for understanding the processes that control modern tropical vegetation biogeography as well as the environments of early humans across Africa. Finally, this work highlights the resilience of montane forests during previous warm intervals, which is relevant for future climate change; however, we point to a fundamental shift in disturbance regimes which are crucial for the structure and composition of modern East African landscapes.

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Land use changes in an afrotropical biodiversity hotspot affect stream alpha and beta diversity

Cited by 44 publications

References 82 publications

Taxonomic, functional, and phylogenetic β‐diversity patterns of stream fish assemblages in tropical agroecosystems

Taxonomic, functional, and phylogenetic β‐diversity patterns of stream fish assemblages in tropical agroecosystems

Beta diversity response to stress severity and heterogeneity in sensitive versus tolerant stream diatoms

Waxing and waning of forests: Late Quaternary biogeography of southeast Africa

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