Latitudinal patterns and regionalization of plant diversity along a 4270‐km gradient in continental Chile

According to the global latitudinal diversity gradient, a decrease in animal and plant species richness exists from the tropics towards higher latitudes. The aim of this study was to describe the latitudinal distribution patterns of Chilean continental flora and delineate biogeographic regions along a 4270‐km north–south gradient. We reviewed plant lists for each of the 39 parallels of continental Chile to build a database of the geographical distribution of vascular plant species comprising 184 families, 957 genera and 3787 species, which corresponded to 100%, 94.9% and 74.2% of the richness previously defined for Chile, respectively. Using this latitudinal presence–absence species matrix, we identified areas with high plant richness and endemism and performed a Cluster analysis using Jaccard index to delineate biogeographic regions. This study found that richness at family, genus and species levels follow a unimodal 4270‐km latitudinal distribution curve, with a concentration of richness in central Chile (31–42°S). The 37th parallel south (central Chile) presented the highest richness for all taxonomic levels and in specific zones the endemism (22–37°S) was especially high. This unimodal pattern contrasts the global latitudinal diversity gradient shown by other studies in the Northern hemisphere. Seven floristic regions were identified in this latitudinal gradient: tropical (18–22°S), north Mediterranean (23–28°S), central Mediterranean (29–32°S), south Mediterranean (33–37°S), north temperate (38–42°S), south temperate (43–52°S) and Austral (53–56°S). This regionalization coincides with previous bioclimatic classifications and illustrates the high heterogeneity of the biodiversity in Chile and the need for a reconsideration of governmental conservation strategies to protect this diversity throughout Chile.     

云南树干附生苔藓生物量沿纬度及海拔梯度的变化特征

为探讨不同森林群落树干附生苔藓的生物量及其组成沿纬度、海拔梯度的变化格局,采用样地调查法,对云南热带(勐腊县)、亚热带(镇沅县)及亚高山(丽江玉龙县)不同海拔不同森林类型中树干附生苔藓的总生物量、优势组分生物量和不同生活型组分生物量的分布格局进行调查研究。结果表明:(1)随着纬度、海拔的升高,3种代表性森林类型单位面积树干附生苔藓植物的生物量上升,以丽江亚高山针叶林最高(3.57 g·400 cm~(-2));镇沅亚热带常绿阔叶林次之,为2.00 g·400 cm~(-2);勐腊热带森林最低,仅为0.53 g·400 cm~(-2)。(2)3种森林类型树干附生苔藓植物的优势组分中无相同物种。(3)随着纬度、海拔的上升,单位面积附生苔藓植物平均生物量上升,优势种类的相对生物量占比有所下降,勐腊热带森林、镇沅哀牢山亚热带常绿阔叶林和丽江玉龙雪山亚高山针叶林树干附生苔藓优势组分的生物量分别占总生物量的92.3%、75.6%和85.2%。(4)随着纬度和海拔的上升,3种森林类型树干附生苔藓植物群落不同生活型组分的生物量存在明显的分异规律。细平铺型、扇形和丛集型分别为勐腊热带森林、镇沅哀牢山亚热带常绿阔叶林和丽江玉龙雪山亚高山针叶林的优势附生苔藓生活型。     

Latitudinal pattern in plant composition along the Peruvian and Chilean fog oases

Fog oases in western South America (locally named lomas) are distributed in a kind of fragmented or patchy way into the coastal desert. Their origin, as well as their current ecological connections in terms of species' dispersal capability, remains an open question. We analyzed the latitudinal pattern in plant species and phylogenetic similarities of 13 lomas, which cover the latitudinal extent of these habitats, from 7°58′ to 26°15′ S. A data-set of 1004 species from available checklists was considered. Plant species composition and phylogenetic relationships among lomas were analyzed by non-metric multidimensional scaling. Our results show three main groups of lomas (northern Peruvian, southern Peruvian, and North-Central Chilean lomas) that are aligned along a complex, nonlinear north–south gradient in ordination space. The weak species overlap between Peruvian and Chilean lomas, together with the higher content in endemic species of the Chilean communities, supports the hypothesis that, at least recently, species composition of the three main groups of lomas has been shaped by desert barriers limiting plant dispersal.     

Latitudinal Variation in Termite Species Richness and Abundance along the Brazilian Atlantic Forest Hotspot

In this study, we investigated the termites of the Brazilian Atlantic Forest, one of the most threatened biodiversity hotspots in the world, in regularly spaced sites from 7° S to 27° S latitude. To our knowledge, this is the only report of a latitudinal survey of termites at species level performed with a standardized sampling protocol. We evaluate termite diversity and abundance, and describe patterns of species composition based on feeding groups along the latitudinal gradient. We also describe the relative contribution of environmental variables to explain diversity patterns. Termite assemblages were investigated by standardized surveys at 15 Atlantic Forest sites, on six transects divided into five sections of 10 m², with 30 sections per site (or 300 m²/site), which were investigated by one trained person for one hour. Observed species richness and abundance were negatively correlated with latitude. The influence of latitude was explained mainly by variables related to temperature, precipitation and ambient energy (potential evapotranspiration). Our results also suggest that temperature exerts a greater constraint on Atlantic Forest termites than productivity, because ambient productivity increases with latitude in this forest but termite diversity decreases. Termite species richness in the Atlantic Forest showed a different pattern than those described for other organisms, increasing in diversity where the coastal‐forest strip narrows. Overall, our results indicate comparatively high termite species richness at northeastern sites and a significant impoverishment of termite assemblages in the southeastern and southern regions of the Atlantic Forest.     

Haematozoa in forest birds from southern Chile: Latitudinal gradients in prevalence and parasite lineage richness

Abstract The existence of latitudinal gradients in species richness and their abundance is known for many free living organisms but few cases have been reported for parasitic diseases. In addition, asymmetries between the Northern and Southern Hemispheres in several characteristics may affect the distribution and diversity of species at all ecological levels. In this respect, we study the distribution of several genera of blood parasites infecting birds along a latitudinal gradient that includes the world's southernmost forests ecosystems. Birds were mist‐netted and sampled for blood in localities across Chile ranging from 33°S to 55°S during the years 2003–06. Overall, 26 bird species were sampled and 27 parasite lineages were identified. The latter belonged to three genera: Plasmodium (8), Haemoproteus (8) and Leucocytozoon (11). We found a positive significant relationship between prevalence and latitude for Leucocytozoon lineages and a negative relationship for Haemoproteus, Plasmodium and mixed infections. However, we did not find a significant relationship between parasite diversity and latitude. We found 18 lineages infecting only one species of host, and 19 lineages appear in only one of the localities of sampling. This pattern implies that some parasite lineages may evolve in isolation in some species/localities. In addition, specificity at the host‐family level was only found for Haemoproteus lineages infecting birds in the family Emberizidae. Individuals of the long distance migrant bird white‐crested elaenia (Elaenia albiceps), were found infected by the same parasite lineages in localities separated by 20° of latitude. Infections by these lineages were detected in other sedentary birds including juveniles and nestlings of different bird species. Therefore, long distance migrants are able to distort the presence of latitudinal gradients of diseases due to the potential role of migrants in spreading infections. Geographical gradients in prevalence of avian haematozoa differ between parasite genera and hemispheres, probably in relation to the existence of appropriate vector–parasite–host interactions.     

The zoogeography of algae-associated peracarids along the Pacific coast of Chile

Abstract Aim To describe the zoogeography of the algae‐associated peracarid crustaceans from exposed rocky shores along the SE‐Pacific. Location Chile, 18° S to 42° S. Methods A standardized sampling programme was used at all sites. Samples of macroalgae were taken at twenty sites distributed along the entire study area. Quantitative samples (n = 6 replicates of 8 cm^?2 surface area each) of calcareous and non‐calcareous red algae were taken in the low intertidal, preserved immediately in 4%‐formalin and washed over a 0.2‐mm mesh before sorting. All peracarid individuals were sorted, identified to the species level and then categorized in separate functional groups according to their feeding habits. Graphical representations of species replacement within each functional group along the latitudinal gradient are provided. A classification analysis employing the unweighted paired group method using arithmetic average (UPGMA) was conducted in order to reveal the main zoogeographical zones. Results A total of forty epifaunal peracarid species was found. A gradual replacement of species within different functional groups (grazing and suspension‐feeding species) was observed in the central region (c. 26° S?37° S). In this central region, species with northern and those with southern distribution overlapped, while other species were only found here, resulting in high species richness. The number of species/site/algal species in the northern (north of c. 25.5° S) and southern region (south of c. 38.5° S) was considerably lower than in the central region. The distribution of most grazing peracarids showed a more continuous pattern than that of suspension‐feeding amphipods. The distribution of the remaining species (predators, scavengers, deposit‐feeders, unknowns) was scattered along the examined sites. The cluster analysis for the epifaunal peracarid assemblage confirmed the separation of a northern and southern zone connected by a central (transitional) zone between c. 26° S and c. 37° S. Similar zonation patterns have been found by most other studies on the zoogeography of the Chilean coast, although little agreement exists about the exact limits of this transitional zone. It is discussed that the distribution limits of algae‐associated peracarids (and other macroinvertebrates) – particularly in the transitional zone – may show interannual variations as a result of varying oceanographic conditions. The large affinity of the algae‐associated peracarid fauna from the central and southern Chilean coast to those of other regions indicates that dispersal may be facilitated by rafting with floating algae transported in the Antarctic Circumpolar Current. Main conclusions The zoogeographical analysis of algae‐associated peracarids confirms the existence of a northern and a southern zone connected by an extensive transitional zone. General biology, habitat use and the abundant presence of dispersal vectors such as floating macroalgae may affect the zoogeography of species living in transitional zones with strong interannual variations in current regimes. In these areas, species associated with substrata of high dispersal potential may show different distribution patterns than species inhabiting other substrata.     

Bacteriohopanepolyols along redox gradients in the Humboldt Current System off northern Chile

Marine oxygen minimum zones (OMZs) are characterized by the presence of subsurface suboxic or anoxic waters where diverse microbial processes are responsible for the removal of fixed nitrogen. OMZs have expanded over past decades and are expected to continue expanding in response to the changing climate. The implications for marine biogeochemistry, particularly nitrogen cycling, are uncertain. Cell membrane lipids (biomarkers), such as bacterial bacteriohopanepolyols (BHPs) and their degradation products (hopanoids), have distinctive structural attributes that convey information about their biological sources. Since the discovery of fossil hopanoids in ancient sediments, the study of BHPs has been of great biogeochemical interest due to their potential to serve as proxies for bacteria in the geological record. A stereoisomer of bacteriohopanetetrol (BHT), BHT II, has been previously identified in OMZ waters and has as been unequivocally identified in culture enrichments of anammox bacteria, a key group contributing to nitrogen loss in marine OMZs. We tested BHT II as a proxy for suboxia/anoxia and anammox bacteria in suspended organic matter across OMZ waters of the Humboldt Current System off northern Chile, as well as in surface and deeply buried sediments (125–150 ky). The BHT II ratio (BHT II/total BHT) increases as oxygen content decreases through the water column, consistent with previous results from Perú, the Cariaco Basin and the Arabian Sea, and in line with microbiological evidence indicating intense anammox activity in the Chilean OMZ. Notably, BHT II is transported from the water column to surface sediments, and preserved in deeply buried sediments, where the BHT II ratio correlates with changes in δ¹⁵N sediment values during glacial–interglacial transitions. This study suggests that BHT II offers a proxy for past changes in the relative importance of anammox, and fluctuations in nitrogen cycling in response to ocean redox changes through the geological record.     

Thermal tolerance in the Andean toad Rhinella spinulosa (Anura: Bufonidae) at three sites located along a latitudinal gradient in Chile

Rhinella spinulosa is one of the anuran species with the greatest presence in Chile. This species mainly inhabits mountain habitats and is distributed latitudinally along the western slope of the Andes Range. These habitats undergo great temperature fluctuations, exerting pressure on the amphibian. To identify the physiological strategies and thermal behavior of this species, we analyzed the temperature variables CT_min, CT_max, TTR, τ_heat, and τ_cool in individuals of three sites from a latitudinal gradient (22°S to 37°S). The amphibians were acclimated to 10 °C and 20 °C and fed ad libitum. The results indicate that the species has a high thermal tolerance range, with a mean of 38.14±1.34 °C, a critical thermal maxima of 34.6–41.4 °C, and a critical thermal minima of 2.6–0.8 °C, classifying the species as eurythermic. Furthermore, there were significant differences in CT_máx and TTR only in the northern site. The differences in thermal time constants between sites are due to the effects of size and body mass. For example, those from the central site had larger size and greater thermal inertia; therefore, they warmed and cooled in a slower manner.The wide thermal limits determined in R. spinulosa confirm that it is a thermo-generalist species, a characteristic that allows the species to survive in adverse microclimatic conditions. The level of plasticity in critical temperatures seems ecologically relevant and supports the acclimatization of thermal limits as an important factor for ectothermic animals to adapt to climate change.     

Clonality-Climate Relationships along Latitudinal Gradient across China: Adaptation of Clonality to Environments

Plant clonality, the ability of a plant species to reproduce itself vegetatively through ramets (shoot-root units), occurs in many plant species and is considered to be more frequent in cold or wet environments. However, a deeper understanding on the clonality-climate relationships along large geographic gradients is still scarce. In this study we revealed the clonality-climate relationships along latitudinal gradient of entire China spanning from tropics to temperate zones using clonality data for 4015 vascular plant species in 545 terrestrial communities. Structural equation modeling (SEM) showed that, in general, the preponderance of clonality increased along the latitudinal gradient towards cold, dry or very wet environments. However, the distribution of clonality in China was significantly but only weakly correlated with latitude and four climatic factors (mean annual temperature, temperature seasonality, mean annual precipitation, precipitation seasonality). Clonality of woody and herbaceous species had opposite responses to climatic variables. More precisely, woody clonality showed higher frequency in wet or climatically stable environments, while herbaceous clonality preferred cold, dry or climatically instable environments. Unexplained variation in clonality may be owed to the influences of other environmental conditions and to different clonal strategies and underlying traits adopted by different growth forms and phylogenetic lineages. Therefore, in-depth research in terms of more detailed clonal growth form, phylogeny and additional environmental variables are encouraged to further understand plant clonality response to climatic and/or edaphic conditions.     

Latitudinal gradient of species diversity: multi-scale variability in rocky intertidal sessile assemblages along the Northwestern Pacific coast

This study examined the latitudinal gradient of species diversity of rocky intertidal sessile assemblages on the slopes of rocks along the Northwestern Pacific coast of Japan, located between 31°N and 43°N, by explicitly incorporating an hierarchical spatial scale into the monitoring design. The specific questions were to examine: (1) whether there is a latitudinal gradient of regional diversity, (2) how spatial components of the regional diversity (local diversity and turnover diversity) vary with latitude depending on spatial scale, and (3) whether the latitudinal gradient differs between different measures of species diversity, i.e. species richness and Simpsons diversity index. We measured coverage and the presence or absence of all sessile organisms in a total of 150 census plots established at five shores in each of six regions. The results showed that there were clear latitudinal gradients in regional species richness and in species turnover among shores. However, these patterns were not reflected in smaller-scale local species richness. For Simpsons diversity index, there was no evidence of latitudinal clines either in regional diversity or in spatial components. These results suggest that relative abundance of common species does not vary along latitude, while the number of rare species increases with decreasing latitude.

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An erratum to this article can be found at     

Herbivory Differentially Affects Plant Fitness in Three Populations of the Perennial Herb Lythrum salicaria along a Latitudinal Gradient

Herbivory can negatively and selectively affect plant fitness by reducing growth, survival and reproductive output, thereby influencing plant population dynamics and evolution. Latitudinal variation in intensity of herbivory is common, but the extent to which it translates into corresponding variation in effects on plant performance is still poorly known. We tested the hypothesis that variation in the fitness-consequences of herbivory mirror differences in intensity of herbivory among three natural populations of the perennial herb Lythrum salicaria along a latitudinal gradient from southern to northernmost Sweden. We documented intensity of herbivory and examined its effect on survival, growth and reproductive output over two years by experimentally removing herbivores with insecticide. The intensity of herbivory and the effects of herbivory on plant fitness were strongest in the southern population, intermediate in the central population and weakest in the northern population. The mean proportion of the leaf area removed ranged from 11% in the southern to 3% in the northern population. Herbivore removal increased plant height 1.5-fold in the southern and 1.2-fold in the central population, the proportion plants flowering 4-fold in the southern and 2-fold in the central population, and seed production per flower 1.6-fold in the southern and 1.2-fold in the central population, but did not affect plant fitness in the northern population. Herbivore removal thus affected the relative fecundity of plants in the three populations: In the control, seed output per plant was 8.6 times higher in the northern population compared to the southern population, whereas after herbivore removal it was 2.5 times higher in the southern population. The results demonstrate that native herbivores may strongly affect the demographic structure of L. salicaria populations and thereby shape geographic patterns of seed production. They further suggest that the strength of herbivore-mediated selection varies among populations and decreases towards the north.     

Temperature-Stress Resistance and Tolerance along a Latitudinal Cline in North American Arabidopsis lyrata

The study of latitudinal gradients can yield important insights into adaptation to temperature stress. Two strategies are available: resistance by limiting damage, or tolerance by reducing the fitness consequences of damage. Here we studied latitudinal variation in resistance and tolerance to frost and heat and tested the prediction of a trade-off between the two strategies and their costliness. We raised plants of replicate maternal seed families from eight populations of North American Arabidopsis lyrata collected along a latitudinal gradient in climate chambers and exposed them repeatedly to either frost or heat stress, while a set of control plants grew under standard conditions. When control plants reached maximum rosette size, leaf samples were exposed to frost and heat stress, and electrolyte leakage (PEL) was measured and treated as an estimate of resistance. Difference in maximum rosette size between stressed and control plants was used as an estimate of tolerance. Northern populations were more frost resistant, and less heat resistant and less heat tolerant, but—unexpectedly—they were also less frost tolerant. Negative genetic correlations between resistance and tolerance to the same and different thermal stress were generally not significant, indicating only weak trade-offs. However, tolerance to frost was consistently accompanied by small size under control conditions, which may explain the non-adaptive latitudinal pattern for frost tolerance. Our results suggest that adaptation to frost and heat is not constrained by trade-offs between them. But the cost of frost tolerance in terms of plant size reduction may be important for the limits of species distributions and climate niches.     

Bacterial Community Responses to Soils along a Latitudinal and Vegetation Gradient on the Loess Plateau,China

Soil bacterial communities play an important role in nutrient recycling and storage in terrestrial ecosystems. Loess soils are one of the most important soil resources for maintaining the stability of vegetation ecosystems and are mainly distributed in northwest China. Estimating the distributions and affecting factors of soil bacterial communities associated with various types of vegetation will inform our understanding of the effect of vegetation restoration and climate change on these processes. In this study, we collected soil samples from 15 sites from north to south on the Loess Plateau of China that represent different ecosystem types and analyzed the distributions of soil bacterial communities by high-throughput 454 pyrosequencing. The results showed that the 142444 sequences were grouped into 36816 operational taxonomic units (OTUs) based on 97% similarity. The results of the analysis showed that the dominant taxonomic phyla observed in all samples were Actinobacteria, Proteobacteria, Chloroflexi, Acidobacteria and Planctomycetes. Actinobacteria and Proteobacteria were the two most abundant groups in all samples. The relative abundance of Actinobacteria increased from 14.73% to 40.22% as the ecosystem changed from forest to sandy, while the relative abundance of Proteobacteria decreased from 35.35% to 21.40%. Actinobacteria and Proteobacteria had significant correlations with mean annual precipitation (MAP), pH, and soil moisture and nutrients. MAP was significantly correlated with soil chemical and physical properties. The relative abundance of Actinobacteria, Proteobacteria and Planctomycetes correlated significantly with MAP, suggesting that MAP was a key factor that affected the soil bacterial community composition. However, along with the MAP gradient, Chloroflexi, Bacteroidetes and Cyanobacteria had narrow ranges that did not significantly vary with the soil and environmental factors. Overall, we conclude that the edaphic properties and/or vegetation types are driving bacterial community composition. MAP was a key factor that affects the composition of the soil bacteria on the Loess Plateau of China.     

Archaeal diversity along a subterranean salt core from the Salar Grande (Chile)

The Salar Grande in the Coastal Range of Northern Chile is a fossil evaporitic basin filled with almost pure halite (95% NaCl average). It is assumed that the basin has not received input of brines since the Pliocene (5.3 to 1.8 million years). Below 1 m the halite has remained undissolved since this time, whereas the upper layer has been dissolved and recrystallized by dripping fogs and occasional rainfall. We compared the archaeal community at different depths using both nested PCR and cultivation. The upper 10 cm of halite crust contained diverse haloarchaeal species, including several from new genera, but their provenance is unknown. For samples deeper in the core, a new and rigorous procedure for chemically sterilizing the surface of single halite crystals was developed. These halite crystals contained only species of the genus Halobacterium (Hbt.). Halobacterium salinarum-like sequences were detected by PCR, and evidence that they were from ancient DNA include: comparison with numerous negative controls; detection of 16S rRNA sequence differences in non-conserved regions, indicating genuine evolutionary mutations rather than PCR-cloning artefacts; independent isolation of Hbt. salinarum from ancient halite; and diverse mechanisms possessed by this species for minimizing radiation damage and thus enhancing its potential for long-term survival. Haloarchaea related to Hbt. noricense were obtained from enrichment cultures from ≈ 0.4 and 15.4 m depth. We investigated Hbt. noricense strain A1 and found that when trapped inside halite crystals its recovery was as rapid after 27 months of entombment as at day 0, faring much better than other extreme halophiles. A biogeographical investigation showed that Hbt. noricense-like organisms were: commonly found in surface-sterilized ancient halite, associated with salt mines, in halite crusts, and, despite a much more intense search, only rarely detected in surface environments. We conclude that some Halobacterium species are specialists at long-term survival in halite.     

Size variation ofAcacia caven (leguminosae) pods along a climatic gradient in Chile

A southward tendency of increment in pod-length is shown for 11 populations ofAcacia caven (Mol.) Hook et Arn. localized along a climatic gradient of increasing annual rainfall in Chile. This fact would suggest thatA. caven populations occurring in the south are in better conditions for reproduction than northern populations, since pod-length is related to the amount of seeds inside the pods. The possible bearing of this southward tendency of increasing seed production upon the expansion ofA. caven toward the more humid zones in southern Chile is discussed.     

Thermal biology of the fossorial rodent Ctenomys fulvus from the Atacama desert, northern Chile

The Andean tuco-tuco, Ctenomys fulvus (Rodentia: Ctenomyidae) inhabits one of the most arid regions of the world, the Salar de Atacama, Northeast of Antofagasta, Chile (23°17′06″S, 68°05′43″W; 2.240 m.a.s.l). We found that a stable microclimate in burrows, a low evaporative water loss (EWL), and a diet of roots (59% water content) are the main factors that permit the survival of this fossorial species in harsh desert conditions. Large circadian variation in T_a was observed above ground. Daily ΔT_a (T_a max − T_a min) = 37.9±0.2°C in summer and in winter. In contrast, circadian variation of T_a inside the burrows was only 5.8±0.5°C in the same seasons. Relative humidity (RH) was 1.9–3.1% during the day, increasing to maximum values of 27% at night and early morning. Inside the burrows RH was higher and quite stable, ranging between 53.1 and 65%, independent of the time of day and season. EWL, measured between 10 and 25°C, was low (1.26 mg/g h), and a moderate increase of 13–20% was observed at higher temperatures. The low EWL may prevent dehydration. However, because of the low heat loss capability, animals became hyperthermic (0.8–1.6°C) in dry air at T_a=30–35°C. As T_a during afternoon normally exceeded 35°C, the microclimate of burrows provided the only way to avoid the lethal effects of hyperthermia.