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opencc-zeroNov 2023View details →

Is there a latitudinal diversity gradient for symbiotic microbes? A case study with sensitive partridge peas

Mutualism is thought to be more prevalent in the tropics than temperate zones and may therefore play an important role in generating and maintaining high species richness found at lower latitudes. However, results on the impact of mutualism on latitudinal diversity gradients are mixed, and few empirical studies sample both temperate and tropical regions. We investigated whether a latitudinal diversity gradient exists in the symbiotic microbial community associated with the legume Chamaecrista nictitans. We sampled bacteria DNA from nodules and the surrounding soil of plant roots across a latitudinal gradient (38.64 °N to 8.68 °N). Using 16S rRNA sequence data, we identified many non-rhizobial species within C. nictitans nodules that cannot form nodules or fix nitrogen. Species richness increased towards lower latitudes in the non-rhizobial portion of the nodule community but not in the rhizobial community. The microbe community in the soil did not effectively predict the non-rhizobia community inside nodules, indicating that host selection is important for structuring non-rhizobia communities in nodules. We next factorially manipulated the presence of three non-rhizobia strains in greenhouse experiments and found that co-inoculations of non-rhizobia strains with rhizobia had a marginal effect on nodule number and no effect on plant growth. Our results suggest that these non-rhizobia bacteria are likely commensals – species that benefit from associating with a host but are neutral for host fitness. Overall, our study suggests that temperate C. nictitans plants are more selective in their associations with the non-rhizobia community, potentially due to differences in soil nitrogen across latitude.

Table 1 in Latitudinal Diversity Gradients in Free-living Microorganisms - Hoogenraadia a Key Genus in Testate Amoebae Biogeography

Table 1. Characters and distribution of six species of the genus Hoogenraadia (L – length, W – width). Many of the earlier papers do not report a sample size for number of tests measured – so it is possible that some of these data may be based on a very low sample size.<table><tbody><tr><th>Species</th><th>Size (µm)</th><th>Distribution regions and publication</th><th>Habitats</th></tr></tbody><tbody><tr><th>H. africana</th><td>L = 95–115, W = 47–60</td><td>Moyen-Congo (Gauthier-Lièvre and Thomas 1958), Guinea and Equatorial Guinea (Golemansky 1962), Brasil (Leiptniz et al. 2003), China (Qin et al. 2011)</td><td>Sphagnum, water, river, forest marsh</td></tr><tr><th>H. asiatica</th><td>L = 95, W = 70</td><td>China (Wang and Min 1987)</td><td>Quaternary deposit</td></tr><tr><th>H. cryptostoma</th><td>L = 130–140, W = 105–110</td><td>Moyen-Congo (Gauthier-Lièvre and Thomas 1958), States of Parana, Mato Grosso du Sul, Brasil (Velho et al. 1996, 2000)</td><td>Swamp quite shady in the bed of a stream</td></tr><tr><th>H. humicola</th><td>L = 143–146, W = 96–100</td><td>Nepal, Himalayas (Bonnet 1977, 1978), Philippines (Bonnet 1980), Cote d’Ivoire, Africa (Bonnet 1976, 1978), Tonga and Western Samoa Islands (Korganova 1994), China (this paper)</td><td>Soils rich in organic debris in forest-gallery backwaters. The ground litter and sublitter horizons of white subtropical soils</td></tr><tr><th>H. ovata</th><td>L = 60–67, W = 36–39</td><td>Cote d’Ivoire, Africa (Bonnet 1976)</td><td>Soils rich in organic debris in forest-gallery backwaters</td></tr><tr><th>H. sylvatica</th><td>L = 82–93, W = 60–70</td><td>Punta Lara Province of Buenos Aires, Argentina (Vucetich 1974)</td><td>Moss in marginal forest</td></tr></tbody></table>

opencc-zeroAug 2022View details →

Exceptions to the rule: Relative roles of time, diversification rates and regional energy in shaping the inverse latitudinal diversity gradient

Aim: Inverse latitudinal diversity gradients (i-LDG), whereby regional richness peaks outside the tropics, have rarely been investigated and their causes remain unclear. Here, we investigate three prominent explanations, postulating that species-rich regions have had (1) longer time to accumulate species, (2) faster diversification, and (3) more energy to support more diverse communities. These mechanisms have been shown to explain the tropical megadiversity, and we examine whether they can also explain i-LDG. Location: Global Time period: Contemporary Major taxa studied: Amphibians, birds, mammals Methods: We estimated the time for species accumulation, regional diversification rates, and regional energy for six tetrapod taxa (≈ 800 species). Then, we quantified the relative effects and interactions among these three classes of variables, using variance partitioning, and confirmed the results across alternative metrics for time (community phylometrics and BioGeoBEARS), diversification rates (BAMM and DR), and regional energy (past and current temperature, productivity). Results: While regional richness across each of the six taxa peaked in the temperate region, it varied markedly across hemispheres and continents. The effects of time, diversification rates, and regional energy varied greatly from one taxon to another, but high diversification rates generally emerged as the best predictor of high regional richness. The effects of time and regional energy were limited, with the exception of salamanders and cetaceans. Main conclusions: Together, our results indicate that the causes of i-LDG are highly taxon-specific. Consequently, large-scale richness gradients might not have a universal explanation and different causal pathways might converge on similar gradients. Moreover, regional diversification rates might vary dramatically between similar environments and, depending on the taxon, regional richness might or might not depend on the time for species accumulation. Together, these results underscore the complexity behind the formation of richness gradients, which might involve a symphony of variations on the interplay of time, diversification rates, and regional energy.

opencc-zeroOct 2022View details →

Examining the diversity, stability and functioning of marine fish communities across a latitudinal gradient

Aim: As anthropogenic stressors on the biosphere intensify, understanding how communities respond to disturbances is critical. Biodiversity is often thought to promote the stability of communities over time and enhance ecosystem functioning. However, results have been inconsistent, and the multifaceted linkages among diversity, stability, and functioning under acute disturbances remain poorly understood. We experimentally tested the responses of marine fish communities to disturbance (i.e., acute habitat loss) across a diversity gradient spanning 35º degrees of latitude in the western Atlantic Ocean to assess the diversity-stability relationship and the interplay between diversity, stability, and fish biomass recovery (as a proxy for function) in marine fish communities. Location: Western Atlantic Ocean (Maine, Massachusetts, North Carolina, Florida [USA], Belize, and Panama). Time period: 2016 – 2017 Major taxa studied: Small, bottom-dwelling ('cryptobenthic') fishes Results: Diversity showed a negative effect on community stability at both the regional (across docks) and local (within docks) scales. Similarly, local diversity was negatively correlated with ecosystem function. These effects are exacerbated by the habitat loss imposed via our experimental treatment. Main conclusions: Our results suggest that habitat loss may more intensively re-shuffle diverse, tropical communities, which impacts biomass recovery, our proxy of functioning. Contrary to ecological theory, in small-bodied, benthos-associated vertebrate communities, biodiversity may neither promote stability nor functioning, suggesting that human disturbances may be particularly impactful in tropical, high-diversity ecosystems.

opencc-by-4.0Aug 2024View details →

Fig. 2 in Elucidating nematode diversity and prevalence in moose across a wide latitudinal gradient using DNA metabarcoding

Fig. 2. Nematode component community in winter with a) the number of nematode taxa detected at each study area and b) the number of nematode taxa shared among study areas.

opencc-by-4.0Aug 2024View details →

Fig. 3 in Elucidating nematode diversity and prevalence in moose across a wide latitudinal gradient using DNA metabarcoding

Fig. 3. Prevalence in each study area of the six most common nematodes detected. Whiskers indicate 95% confidence intervals.

opencc-by-4.0Aug 2024View details →

Fig. 1. A in Elucidating nematode diversity and prevalence in moose across a wide latitudinal gradient using DNA metabarcoding

Fig. 1. A map showing the distribution of the five study areas across Norway ranging from 59.6◦N to 70.5◦N.

opencc-zeroDec 2022View details →

Patterns of functional diversity along latitudinal gradients of species richness in eleven fish families

Aim: As we enter an era of major biodiversity shifts, understanding large-scale biodiversity patterns has become crucial for ecological and conservation purposes. Often, conservation priorities are based on concepts derived largely from species richness, yet recent works show that different facets of biodiversity are also critical for proper ecosystem continuity, function, and services. One facet of biodiversity increasingly relevant to conservation is functional diversity. Here, we aim to improve our understanding of large-scale patterns of biodiversity by testing the hypothesis that species richness can also accurately estimate functional diversity along the latitudinal gradient of species richness in fish. Location: Marine Environments. Time Period: Contemporary Major taxa studied: 842 species within eleven fish families; Acanthuridae, Blenniidae, Chaetodontidae, Gobiidae, Labridae, Lutjanidae, Pleuronectidae, Pomacanthidae, Pomacentridae, Scombridae, Sparidae. Methods: Using geometric morphometrics to calculate morphological diversity, a proxy for functional diversity, we estimated expected functional diversity for a given number of species and compared it to the observed functional diversity in fish families along latitudes. We then fit a brokenstick regression model with estimates of functional diversity over absolute degree of latitudes to locate latitudes where significant shifts in functional diversity occur. Results: We found that species richness typically over- or under-estimated functional diversity along the latitudinal gradient of species richness in the evaluated fishes. We also show that for most families investigated, there is a pattern of stable functional diversity from the equator through the tropics that shifts with a mean inflection point occurring at absolute latitude 31.7° ± 10.1°. We suggest this pattern may be linked to changes in environmental factors such as global temperature and/or habitat availability beyond tropical latitudes, however, these concepts require more study. Main conclusion: This analysis shows the importance of further considering functional diversity in combination with other biodiversity metrics when developing conservation priorities and policies.

opencc-by-4.0Aug 2023View details →

Replication Data for: "Marine latitudinal diversity gradients are generally absent in intertidal ecosystems"

Datasets used in the paper "Marine latitudinal diversity gradients are generally absent in intertidal ecosystems"

Fig. 1. SEM photos showing c.f in Latitudinal Diversity Gradients in Free-living Microorganisms - Hoogenraadia a Key Genus in Testate Amoebae Biogeography

Fig. 1. SEM photos showing c.f. Hoogenraadia humicola found from soils in Shennongjia Mountains of central China (the left picture is from Qin et al. 2011). This was previously identified as Planhoogenraadia africana by Qin et al. (2011). Scale bars: 50 µm (a) and 20 µm (b).

Fig. 3 in Latitudinal Diversity Gradients in Free-living Microorganisms - Hoogenraadia a Key Genus in Testate Amoebae Biogeography

Fig. 3. Relationship between shell width and shell length of each species of the genus Hoogenraadia. The sample sizes on which these measurements are based is unclear as the older literature often doesn't specify the number of tests measured (see Table 1).

Fig. 2 in Latitudinal Diversity Gradients in Free-living Microorganisms - Hoogenraadia a Key Genus in Testate Amoebae Biogeography

Fig. 2. Shell outline and SEM photos of six species of genus Hoogenraadia Gauthier-Lièvre and Thomas 1958, with scale bar 50 μm. a – H. cryptostoma Gauthier-Lièvre and Thomas 1958; b – H. sylvatica Vucetich 1974; c – H. africana Gauthier-Lièvre and Thomas 1958; d – H. humicola Bonnet 1976; e – H. ovata Bonnet 1976; f – H. asiatica Wang and Min 1987.