Cryptic species diversity reveals biogeographic support for the ‘mountain passes are higher in the tropics’ hypothesis

Gill, Brian A.; Kondratieff, Boris C.; Casner, Kayce L.; Encalada, Andrea C.; Flecker, Alexander S.; Gannon, Dustin G.; Ghalambor, Cameron K.; Guayasamín, Juan M.; Poff, N. LeRoy; Simmons, Mark P.; Thomas, Steven A.; Zamudio, Kelly R.; Funk, W. Chris

doi:10.1098/rspb.2016.0553

Cited by 82 publications

(86 citation statements)

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“…Further, our findings of a monotonic decrease in the thermal optima and lower minima of species and communities located at higher elevations, partially confirms our second hypothesis (Figures b and b). Yet, we found no relationship between species niche breadths and elevation nor with community breadth score and elevation, as opposed to Janzen's hypothesis (Janzen, ) and the results recently reported for cryptic aquatic insects (Gill et al, ). This suggests that the seasonality gradient is more strongly associated with species and community thermal niche breadth than summit elevation in tropical alpine systems.…”

Section: Discussioncontrasting

confidence: 99%

“…We suspect the lack of annual thermal seasonality in equatorial mountain summits creates more constant conditions throughout the year, which could allow the presence of a more diverse array of biogeographical species groups including Tropical montane, Tropical Andean alpine and Páramo endemic species (Figure c). Complementary, the results of Gill et al () that shows the effect of the CVH along the elevation gradients became evident when only the cryptic species were considered in the analyses. Thus, a similar pattern could arise in our dataset if we only look at narrow‐range species restricted to alpine habitats across the Andes.…”

Section: Discussionmentioning

confidence: 62%

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Thermal niche traits of high alpine plant species and communities across the tropical Andes and their vulnerability to global warming

Cuesta

Tovar

Llambí

et al. 2019

Journal of Biogeography

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Aim The climate variability hypothesis (CVH) predicts that locations with reduced seasonal temperature variation select for species with narrower thermal ranges. Here we (a) test the CVH by assessing the effect of latitude and elevation on the thermal ranges of Andean vascular plant species and communities, and (b) assess tropical alpine plants vulnerability to warming based on their thermal traits. Location High tropical Andes. Taxon Vascular plants. Methods Temperature data for 505 vascular plant species from alpine communities on 49 summits, were extracted from 29,627 georeferenced occurrences. Species thermal niche traits (TNTs) were estimated using bootstrapping for: minimum temperature, optimum (mean) temperature and breadth (maximum‐minimum). Plant community‐weighted scores were estimated using the TNTs of their constituent species. CVH was tested for species, biogeographical species groups and communities. Vulnerability to global warming was assessed for species, biogeographical species groups and communities. Results Species restricted to the equator showed narrower thermal niche breadth than species whose ranges stretch far from the equator, however, no difference in niche breadth was found across summits’ elevation. Biogeographical species groups distributed close to the equator and restricted to alpine regions showed narrower niche breadth than those with broader ranges. Community‐weighted scores of thermal niche breadth were positively related to distance from equator but not to elevation. Based on their TNTs, species restricted to equatorial latitudes and plant communities dominated by these species were identified as the most vulnerable to the projected 1.5°C warming, due to a potentially higher risk of losing thermal niche space. Main conclusions Our study confirms that the CVH applies to high tropical Andean plant species and communities, where latitude has a strong effect on the thermal niche breadth. TNTs are identified as suitable indicators of species’ vulnerability to warming and are suggested to be included in long‐term biodiversity monitoring in the Andes.

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Section: Discussioncontrasting

confidence: 99%

Section: Discussionmentioning

confidence: 62%

Thermal niche traits of high alpine plant species and communities across the tropical Andes and their vulnerability to global warming

Cuesta

Tovar

Llambí

et al. 2019

Journal of Biogeography

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“…The authors found that cryptic species were homogeneously distributed among taxa and regions and concluded “that cryptic metazoan diversity can be treated as random error in biodiversity assessments.” Their meta‐analysis was later criticized for several methodological problems (Trontelj & Fišer, ), and additional analyses almost a decade later suggested that cryptic species actually may be heterogeneously distributed across animal phyla (Pérez‐Ponce de León & Poulin, ). The evidence for homogenous distribution of cryptic species across geographic regions is conflicting (Eme et al., ; Gill et al., ; Voda, Dapporto, Dinca, & Vila, ); perhaps an heterogeneous distribution can be detected only at global geographic scales.…”

Section: Cryptic Diversity In Biodiversity Researchmentioning

confidence: 99%

Cryptic species as a window into the paradigm shift of the species concept

2018

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The species concept is the cornerstone of biodiversity science, and any paradigm shift in the delimitation of species affects many research fields. Many biologists now are embracing a new "species" paradigm as separately evolving populations using different delimitation criteria. Individual criteria can emerge during different periods of speciation; some may never evolve. As such, a paradigm shift in the species concept relates to this inherent heterogeneity in the speciation process and species category-which is fundamentally overlooked in biodiversity research. Cryptic species fall within this paradigm shift: they are continuously being reported from diverse animal phyla but are poorly considered in current tests of ecological and evolutionary theory. The aim of this review is to integrate cryptic species in biodiversity science. In the first section, we address that the absence of morphological diversification is an evolutionary phenomenon, a "process" counterpart to the long-studied mechanisms of morphological diversification. In the next section regarding taxonomy, we show that molecular delimitation of cryptic species is heavily biased towards distance-based methods. We also stress the importance of formally naming of cryptic species for better integration into research fields that use species as units of analysis. Finally, we show that incorporating cryptic species leads to novel insights regarding biodiversity patterns and processes, including large-scale biodiversity assessments, geographic variation in species distribution and species coexistence. It is time for incorporating multicriteria species approaches aiming to understand speciation across space and taxa, thus allowing integration into biodiversity conservation while accommodating for species uncertainty.

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“…As a consequence, we can predict that physiological barriers to dispersal will be stronger for thermally specialized forest species, and as a corollary, forest species will have narrower elevational ranges than open‐habitat species (Ghalambor et al., ; Sheldon et al., ). Janzen's hypothesis pertains latitudinal comparisons between mountains (Gill et al., ; Polato et al., ). Our hypothesis is derived from the same underlying physiological principle; species are adapted to temperatures normally encountered in their temporal and geographical habitat or microhabitat (Janzen, ).…”

Section: Introductionmentioning

confidence: 99%

Elevational and microclimatic drivers of thermal tolerance in Andean Pristimantis frogs

Pintanel

Tejedo

Ron

et al. 2019

Journal of Biogeography

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Aim We analysed elevational and microclimatic drivers of thermal tolerance diversity in a tropical mountain frog clade to test three macrophysiological predictions: less spatial variation in upper than lower thermal limits (Bretts’ heat‐invariant hypothesis); narrower thermal tolerance ranges in habitats with less variation in temperature (Janzen's climatic variability hypothesis); and higher level of heat impacts at lower elevations. Location Forest and open habitats through a 4,230‐m elevational gradient across the tropical Andes of Ecuador. Method We examined variability in critical thermal limits (CTmax and CTmin) and thermal breadth (TB; CTmax–CTmin) in 21 species of Pristimantis frogs. Additionally, we monitored maximum and minimum temperatures at the local scale (tmax, tmin) and estimated vulnerability to acute thermal stress from heat (CTmax–tmax) and cold (tmin–CTmin), by partitioning thermal diversity into elevational and microclimatic variation. Results Our results were consistent with Brett's hypothesis: elevation promotes more variation in CTmin and tmin than in CTmax and tmax. Frogs inhabiting thermally variable open habitats have higher CTmax and tmax and greater TBs than species restricted to forest habitats, which show less climatic overlap across the elevational gradient (Janzen's hypothesis). Vulnerability to heat stress was higher in open than forest habitats and did not vary with elevation. Main conclusions We suggest a mechanistic explanation of thermal tolerance diversity in elevational gradients by including microclimatic thermal variation. We propose that the unfeasibility to buffer minimum temperatures locally may explain the rapid increase in cold tolerance (lower CTmin) with elevation. In contrast, the relative invariability in heat tolerance (CTmax) with elevation may revolve around the organisms’ habitat selection of open‐ and canopy‐buffered habitats. Secondly, on the basis of microclimatic estimates, lowland and upland species may be equally vulnerable to temperature increase, which is contrary to the pattern inferred from regional interpolated climate estimators.

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Cryptic species diversity reveals biogeographic support for the ‘mountain passes are higher in the tropics’ hypothesis

Cited by 82 publications

References 82 publications

Thermal niche traits of high alpine plant species and communities across the tropical Andes and their vulnerability to global warming

Thermal niche traits of high alpine plant species and communities across the tropical Andes and their vulnerability to global warming

Cryptic species as a window into the paradigm shift of the species concept

Elevational and microclimatic drivers of thermal tolerance in Andean Pristimantis frogs

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