Stability of Afromontane ant diversity decreases across an elevation gradient

Joseph, Grant S.; Muluvhahothe, Mulalo M.; Seymour, Colleen L.; Munyai, Thinandavha C.; Bishop, Tom R.; Foord, Stefan H.

doi:10.1016/j.gecco.2019.e00596

Cited by 9 publications

(11 citation statements)

References 32 publications

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“…This result is somewhat surprising, especially because there is a significant change in the richness and composition of ant species with the advance of the successional secondary vegetation (Marques et al., 2017; Neves et al., 2013). Studies carried out in savannas and mountain ecosystems have found that greater habitat complexity should minimize the variation of ant diversity over time (Joseph et al., 2019; Mauda et al., 2018; Tiede et al., 2017), which is contrary to our finding of high variation even in the late stage. However, it is important to note that tropical dry forests are strongly seasonal, and the ant fauna might have evolved to cope with natural variations under these habitat conditions.…”

Section: Discussioncontrasting

confidence: 99%

“…This approach therefore has considerable potential for addressing the influence of both the successional stage and strata on ant communities. Ecological stability, the inverse of variation over time, is a fundamental ecosystem property that offers insights into biodiversity and ecosystem processes (Doak et al., 1998; Joseph et al., 2019; Tonkin et al., 2017). Critically, β‐diversity can be decomposed into the turnover and nestedness components, which provide complementarity insights into community ecological stability: the turnover component reflects species replacement, while the nestedness component reflects species richness differences driven by a pattern of community subsetting (Baselga, 2010).…”

Section: Introductionmentioning

confidence: 99%

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Spatiotemporal dynamics of the ant community in a dry forest differ by vertical strata but not by successional stage

et al. 2021

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Ants are diverse and ecologically important organisms in tropical forests, where their spatiotemporal distribution can be highly complex. This complexity arises mainly from marked differences in microclimatic conditions and resource availability through space and time that is even more evident in highly seasonal environments, such as tropical dry forests. However, it is unclear how seasonality interacts with other factors that might shape temporal variation of ant composition (β-diversity), like vertical strata and habitat disturbance. Our goal was to examine the potential influence of vertical stratification and the successional stage on the spatiotemporal variation of a tropical dry forest's ant species composition. We assessed whether species turnover or nestedness was the main component determining the spatiotemporal β-diversity of ant communities across the canopy and litter strata. We sampled canopy and litter ants in ten plots, half in the early and half on the late stage of secondary succession at four times, twice in wet and twice in dry season. A high species turnover defined the spatiotemporal β-diversity of canopy and litter ant communities across years and seasons in our focal dry forests. Importantly, the temporal ant species composition was much more stable in the canopy than in the litter. Moreover, we found that the ant community's temporal dynamics was consistently high across successional stages, not differing in the temporal β-diversity between early and late succession. Our results provide valuable insights into the potential underlying causes of community assembly and spatiotemporal dynamics in seasonal habitats, like the highly threatened and diverse tropical dry forests.

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Section: Discussioncontrasting

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Spatiotemporal dynamics of the ant community in a dry forest differ by vertical strata but not by successional stage

et al. 2021

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“…Recent models reveal contraction of species’ ranges at higher elevation from montane regions in two southern African countries 4 . In our study site, ants show a decrease in species diversity with increasing altitude 18 , and at higher altitude sites, diversity over time seems to be more variable 31 . Here, we assess whether ant species composition across elevational gradients changes owing to species turnover or species loss, by assessing the relative contribution of these two components to beta diversity over 6 years.…”

Section: Introductionmentioning

confidence: 52%

“…With global change, there is growing interest in how FD varies across environmental gradients 33 , 36 , 37 . Given that heating could be associated with changes to species composition and the number of species, particularly at altitude 31 , patterns of FD with altitude and aspect may give insights into whether and how the role of ants in ecosystem functioning might change, or whether species are merely replaced by functional analogues along abiotic or biotic gradients. At environmental extremes, resources are increasingly limited, which can amplify environmental filtering 38 , 39 .…”

Section: Introductionmentioning

confidence: 99%

Repeated surveying over 6 years reveals that fine-scale habitat variables are key to tropical mountain ant assemblage composition and functional diversity

Muluvhahothe

Joseph

Seymour

et al. 2021

Sci Rep

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High-altitude-adapted ectotherms can escape competition from dominant species by tolerating low temperatures at cooler elevations, but climate change is eroding such advantages. Studies evaluating broad-scale impacts of global change for high-altitude organisms often overlook the mitigating role of biotic factors. Yet, at fine spatial-scales, vegetation-associated microclimates provide refuges from climatic extremes. Using one of the largest standardised data sets collected to date, we tested how ant species composition and functional diversity (i.e., the range and value of species traits found within assemblages) respond to large-scale abiotic factors (altitude, aspect), and fine-scale factors (vegetation, soil structure) along an elevational gradient in tropical Africa. Altitude emerged as the principal factor explaining species composition. Analysis of nestedness and turnover components of beta diversity indicated that ant assemblages are specific to each elevation, so species are not filtered out but replaced with new species as elevation increases. Similarity of assemblages over time (assessed using beta decay) did not change significantly at low and mid elevations but declined at the highest elevations. Assemblages also differed between northern and southern mountain aspects, although at highest elevations, composition was restricted to a set of species found on both aspects. Functional diversity was not explained by large scale variables like elevation, but by factors associated with elevation that operate at fine scales (i.e., temperature and habitat structure). Our findings highlight the significance of fine-scale variables in predicting organisms’ responses to changing temperature, offering management possibilities that might dilute climate change impacts, and caution when predicting assemblage responses using climate models, alone.

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“…Such a discrepancy probably arises as result of lower taxonomic richness of alpine environments, since temporal stability at the community level cannot be achieved solely by higher asynchrony across species (‘insurance effect’; Naeem & Li, 1997; Yachi & Loreau, 1999), but also by higher species diversity (the so‐called ‘portfolio effect’; Doak et al., 1998). The negative relationship between community stability and elevation provides support for the notion that species richness acts as a buffer against environmental perturbation, which is highly relevant in conservation terms (García‐Palacios et al., 2018; Joseph et al., 2019; Tilman, 1999).…”

Section: Discussionmentioning

confidence: 78%

Spatial heterogeneity in temporal dynamics of Alpine bird communities along an elevational gradient

García‐Navas

Sattler

Özgül

2020

Journal of Biogeography

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Aim Mountains are biodiversity hotspots and are among the most sensitive ecosystems to ongoing global change being thus of conservation concern. Under this scenario, assessing how biological communities vary over time along elevational gradients and the relative effects of niche‐based deterministic processes and stochastic events in structuring assemblages is essential. Here, we examined how the temporal trends of bird communities vary with elevation over a 20 year‐period (1999–2018). We also tested for differences in temporal dynamics among habitat types (among‐community variability) and functional groups (within‐community variability). Taxon 97 species of common breeding birds. Location Swiss Alps. Methods We used abundance data from the Swiss breeding bird survey to compute different temporal dynamic metrics (temporal turnover, synchrony, rate of community change and community‐level of covariance among species). We also examined the relative contribution of deterministic and stochastic processes in community assembly using the Raup‐Crick method and the normalized stochasticity ratio. Results We found that, with greater elevation, temporal species turnover increased while the rate of overall community change over successive years decreased, suggesting that high‐elevation communities display more erratic dynamics with no clear trend. Despite this, we found a more deterministic assembly of alpine communities in comparison to those located at lower elevations. Deterministic processes had greater influence than stochastic processes on community assembly along the entire elevational gradient (80% of communities). Forest communities exhibited higher synchrony in comparison to the remaining habitats likely because they consisted of species with greater functional redundancy, whereas alpine communities were the least stable as a result of their low taxonomic richness (‘portfolio’ effect). Main conclusions Community‐level synchrony was overall positive supporting the idea that compensatory mechanisms are rare in natural biological communities. Our results suggest that rather than competition, the existence of differences in the ecological strategies of species may have a stabilizing effect on bird communities by weakening the concordance of species responses to fluctuations in environmental conditions (i.e. enhanced interspecific temporal asynchrony). This study provides evidence that, although species turnover in metacommunities is frequent, a high temporal turnover does not necessarily imply the overriding importance of stochastic processes.

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Stability of Afromontane ant diversity decreases across an elevation gradient

Cited by 9 publications

References 32 publications

Spatiotemporal dynamics of the ant community in a dry forest differ by vertical strata but not by successional stage

Spatiotemporal dynamics of the ant community in a dry forest differ by vertical strata but not by successional stage

Repeated surveying over 6 years reveals that fine-scale habitat variables are key to tropical mountain ant assemblage composition and functional diversity

Spatial heterogeneity in temporal dynamics of Alpine bird communities along an elevational gradient

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