Power laws from the bird species abundance distribution

A recent study found that bird species with fewer individuals are abundant, but large species are rare. We show that this new data strongly suggests a power-law distribution rather than the most accepted log-normal. Moreover, we discuss extinction risk across the bird phylogeny and future conservation efforts by profiting from the hierarchical structure revealed by the new data.

Beta Diversity along an Elevational Gradient at the Pico da Neblina (Brazil): Is Spider (Arachnida-Araneae) Community Composition Congruent with the Guayana Region Elevational Zonation?

Beta diversity is usually high along elevational gradients. We studied a spider community at the Pico da Neblina (Brazil), an Amazonian mountain which is one of the southern components of the Guayana region. We sampled six elevations and investigated if beta diversity patterns correspond to the elevational division proposed for the region, between lowlands (up to 500 m), uplands (500 m to 1500 m), and highlands (>1500 m). Patterns of dominance increased with elevation along the gradient, especially at the two highest elevations, indicating that changes in composition may be accompanied by changes in species abundance distribution. Beta diversity recorded was very high, but the pattern observed was not in accordance with the elevationaldivision proposed for the region. While the highlands indeed harbored different fauna, the three lowest elevationshad similar species compositions, indicating that the lowlands spider community extends into the uplands zone. Other measures of compositional change, such as similarity indices and species indicator analysis, also support this pattern. Our results, in addition to a revision of the literature, confirm the high diversity and endemism rates of montane spider communities, and we stress the importance of protecting those environments, especially considering the climate crisis.

Infestation and Related Ecology of Chigger Mites on the Asian House Rat (Rattus tanezumi) in Yunnan Province, Southwest China

This paper is to illustrate the infestation and related ecological characteristics of chigger mites on the Asian house rat (Rattus tanezumi). A total of 17,221 chigger mites were collected from 2,761 R. tanezumi rats, and then identified as 131 species and 19 genera in 2 families. Leptotrombidium deliense, the most powerful vector of scrub typhus in China, was the first major dominant species on R. tanezumi. All the dominant mite species were of an aggregated distribution among different individuals of R. tanezumi. The species composition and infestations of chiggers on R. tanezumi varied along different geographical regions, habitats and altitudes. The species-abundance distribution of the chigger mite community was successfully fitted and the theoretical curve equation was. Ŝ (R)=37e–(0.28R)2 The total chigger species on R. tanezumi were estimated to be 199 species or 234 species, and this further suggested that R. tanezumi has a great potential to harbor abundant species of chigger mites. The results of the species-plot relationship indicated that the chigger mite community on R. tanezumi in Yunnan was an uneven community with very high heterogeneity. Wide geographical regions with large host samples are recommended in the investigations of chigger mites.

Structure, composition and diversity of restored forest ecosystems on mine-spoils in South-Western Ghana

In response to national policy obligations, many mining companies in Ghana have restored/reclaimed degraded mined out sites through revegetation. The area extent of such restored areas is unknown and there is also paucity of data on success of restoration, species diversity and compositional dynamics of such restored landscapes, particularly using mixed species. This study assessed stand structure, diversity and composition dynamics of sites restored with mixed species and models species abundance distribution on these sites. Three reclaimed and one control site (adjacent natural forest) were inventoried using 27, 30 x 30 m plots on the Hwini-Butre and Benso concession of the Golden Star Wassa Limited. Overall 3057 (per 24 plots) and 150 (per 3 plots) individual trees were recorded in the overstorey of the reclaimed and control sites, respectively. In all, 31 species in 13 families occurred on the reclaimed site while 61 species in 29 families occurred on the control. Species richness, abundance and diversity were significantly lower in the reclaimed sites than the control in the overstorey (p≤0.018), mid-storey (p ≤ 0.032), and understorey (p≤ 0.031). Species composition of the reclaimed and control sites were mostly dissimilar in the overstorey, midstorey, and understorey. However, the midstorey and overstorey of the reclaimed sites showed high similarity in composition (Jaccard’s index = 0.817). Pioneer and shade-tolerant species were most dominant in the understorey of the control while only shade-tolerant species (mostly herbs and grasses) dominated the reclaimed sites. Species abundance distribution of both reclaimed and control sites followed the geometric series model, indicating that both sites are disturbed but at different intensities. It is concluded that reclamation with mixed species does not necessarily lead to rapid restoration of indigenous climax species on mine spoils. Nonetheless, it may lead to accomplishments of short-term goals of stabilizing and protecting landscapes while conditioning the sites for colonisation of the climax species.

Disentangling Environmental Effects on the Tree Species Abundance Distribution and Richness in a Subtropical Forest

As a transitional vegetation type between evergreen broadleaved forest and deciduous broadleaved forest, evergreen-deciduous broadleaved mixed forest is composed of diverse plant species. This distinctive forest is generally distributed in mountainous areas with complex landforms and heterogeneous microenvironments. However, little is known about the roles of environmental conditions in driving the species diversity patterns of this forest. Here, based on a 15-ha plot in central China, we aimed to understand how and to what extent topographical characteristics and soil nutrients regulate the number and relative abundance of tree species in this forest. We measured environmental factors (terrain convexity, slope, soil total nitrogen, and phosphorus concentrations) and species diversity (species abundance distribution and species richness) in 20 m × 20 m subplots. Species abundance distribution was characterized by skewness, Berger–Parker index, and the proportion of singletons. The generalized additive model was used to examine the variations in diversity patterns caused by environmental factors. The structural equation model was used to assess whether and how topographical characteristics regulate species diversity via soil nutrients. We found that soil nutrients had significant negative effects on species richness and positive effects on all metrics of species abundance distribution. Convexity had significant positive effects on species richness and negative effects on all metrics of species abundance distribution, but these effects were mostly mediated by soil nutrients. Slope had significant negative effects on skewness and the Berger–Parker index, and these effects were almost independent of soil nutrients. Soil nutrients and topographical characteristics together accounted for 9.5–17.1% of variations in diversity patterns and, respectively, accounted for 8.9–13.9% and 3.3–10.7% of the variations. We concluded that soil nutrients were more important than topographical factors in regulating species diversity. Increased soil nutrient concentration led to decreased taxonomic diversity and increased species dominance and rarity. Convexity could be a better proxy for soil nutrients than slope. Moreover, these abiotic factors played limited roles in regulating diversity patterns, and it is possible that the observed patterns are also driven by some biotic and abiotic factors not considered here.

Mosquito Species Abundance, Distribution and Diversity in Ughelli North Local Government Area, Delta State, Nigeria

This research was carried out to record mosquito species abundance, distribution, diversity and breeding sites in four villages of Ughelli North Local Government Area of Delta State. Potential habitats of mosquitoes were sampled using dippers, hand-lens and plastic containers between June and November 2014. A total number of 274 sites were examined and only 146 were positive for mosquito larvae. The habitats sampled include domestic containers 107(39.05%), puddles 59(21.53%), tyres 47(17.15%) and drains 61(22.26%). The variation in the number of larvae collected from the various habitats were not significant (P=0.1203, F=2.705 and df= 3). One thousand six hundred and fifty-three (1.653) mosquito larvae were collected and reared to adults. Seven hundred and twelve (712) of the larvae emerged as adults that were separated into three genera: Anopheles, Aedes and culex and identified up to species level. Culex quinquefasciatus was found to be the most abundant (29.35%) in the study area, followed by Aedes aegypti (25.70%). C. nebulosus was the least abundant species with 2.95 %. Domestic containers were the most preferred breeding habitats for all the mosquito species and the variation in the species of mosquito with respect to types of habitat showed significant association in Ofuoma (P=0.0167, F=4.322,df=3) and Adjekota (P=0.0252, F=3.852, df=3). There was significant difference in the occurrence of mosquito species in the month of September (p value 0.0085) compared to June (p value 0.0518), July (p value 0.2370), August (p value 0.1920), October (p value 0.0534) and November (p value 0.0241. Variations existed in the physico-chemical parameters in the different sources of collections in different locations. Temperature ranged from 20.0 to 24.60C while pH (hydrogen ion concentration) range was 6.9 – 7.7 and Dissolved oxygen (D.O) ranged between 1.4 and 2.7(mg/L) as Conductivity ranged between 67.9 and 82.1(μs) and turbidity varied from 62.0NTU in the container samples to 84.2NTU in the gutter samples and depth varied between 6.3 and 68.3(cm) across the different locations but depth ranged from 6.3cm to 68.3cm and temperature was (22.8±2.6), Analysis of variance (ANOVA) and mean was used to determine the significant differences (p<0.05) in habitats and species distribution while Shannon Wiener and Simpson indices were used to determine species diversity and abundance. There is need for concerted efforts in mosquito control in Ughelli North to mitigate the incidence of mosquito transmitted diseases.