Short-term impact of disturbance on genetic diversity and structure of Indonesian populations of the butterfly Drupadia theda in East Kalimantan

We investigated the short‐term impact of disturbance on genetic diversity and structure of the tropical butterfly Drupadia theda Felder (Lepidoptera: Lycaenidae). Populations were sampled from five landscapes in East Kalimantan (Borneo, Indonesia) which were differentially disturbed by selective logging and the 1997/1998 El Niño Southern Oscillation (ENSO)‐induced drought and fires. Sampling occurred before (in 1997) and after the forest fires (in 1998, 1999, 2000, and 2004). Drupadia theda populations underwent serious population size reductions following the 1997/1998 ENSO event. For a total of 208 individuals, we sequenced a 509‐bp segment of mtDNA containing the control region plus the 5’ end of the 12S rDNA gene. Haplotype diversity in D. theda populations ranged from 0.468 to 0.953. Just after the 1997/1998 ENSO event, number of recorded individuals and genetic diversity were very low in D. theda populations sampled in the two severely burned areas and in a small pristine forest fragment that was surrounded by burned forest and thereby affected by drought. Interestingly, higher levels of genetic diversity were observed in logged forest compared to proximate pristine forest. After 1998, the genetic composition within the three ENSO‐disturbed areas diverged. In the twice‐burned forest, the genetic diversity in 1999 already approached pre‐fire levels, while it remained nearly unchanged in proximate once‐burned forest. Our data suggest that the 1997/1998 ENSO‐induced drought and fires caused massive reductions in the genetic diversity of D. theda and that population recoveries were linked to their geographical position relative to patches of unburned forest (and thus to source populations).     

Immediate impact of a hurricane on the structure of a tropical butterfly community

More intense and frequent hurricanes may lead to long‐lasting effects to tropical ecosystems. Here, we describe the immediate impact on the butterfly community of a lowland forest in Belize, following Hurricane Earl. Species richness and abundance increased posthurricane, likely driven by convergence of the organization between the canopy and understory communities.     

Species‐habitat relationships and ecological correlates of butterfly abundance in a transformed tropical landscape

Tropical butterfly conservation strategies often focus on total and/or common species richness to assess the conservation value of a patch or habitat. However, such a strategy overlooks the unique dynamics of rare species. We evaluated the species‐habitat relationships of 209 common, intermediate, and rare butterfly species (including morphospecies) across four habitat types (mature, degraded, or fragmented forest, and urban parks) and two patch sizes (<400 ha, ≥400 ha) in Singapore. Common species richness was consistent across habitat types. Intermediate species richness declined by more than 50 percent in urban parks (relative to all forest habitats), and rare species richness was reduced by 50 percent in degraded and fragmented forest and by 90 percent in urban parks (relative to mature forest). Large patches had comparable overall richness to small patches, but they supported more rare species and three times as many habitat‐restricted species over a similar area. Importantly, a number of rare species were confined to single small patches. Mixed‐effects regression models were constructed to identify habitat and ecological/life history variables associated with butterfly abundance. These models revealed that species with greater habitat specialization, rare larval host plants, few larval host plant genera, and narrow global geographic ranges were more likely to be rare species. Overall, these results demonstrate that the richness of habitat‐restricted and rare species do not follow the same spatial distribution patterns as common species. Therefore, while conserving mature forests is key, effective butterfly conservation in a transformed landscape should take into account rare and habitat‐restricted species.     

Protandry and female size-fecundity variation in the tropical butterfly Brassolis sophorae

Protandry (the emergence of males before females) is currently explained either as a mating strategy to maximize number of matings in the males, or a way to minimize pre-reproductive mortality in females. Models of protandry have generally ignored variation in female quality (reproductive potential). We recorded the sex ratio, female body mass, wing length and potential fecundity (number and mass of eggs) of the tropical butterfly Brassolis sophorae through the emergence period. Temporal variation in female size and fecundity correlated with male potential for acquiring mates. Females from the end of the emergence period showed lower fecundity and size. Males emerging before and close to the median date of the female emergence period had greater mating opportunities. Males emerging either very early or late were penalized by few mating opportunities, or by encounters with small, low-quality females, respectively. Received: 14 November 1997 / Accepted: 23 March 1998     

High abundance of an exotic amphipod indicates disturbance in tropical rainforests

Previous studies have proposed terrestrial amphipods as potential bioindicators of forest condition. In order to investigate the response of the exotic terrestrial amphipod Talitroides topitotum (Crustacea: Amphipoda: Talitridae) to anthropogenic disturbances and its potential as a bioindicator, we compared its abundance among three forest reserves in southeastern Brazil, under different types and intensities of disturbance. We observed significantly higher abundances in disturbed sites compared to undisturbed sites in two of the reserves sampled, corroborating previous studies. In the third reserve, in which both forest disturbance and the abundance of amphipods were much lower than in the other two reserves, there was no significant difference between the sampling sites. We also speculate about the potential use of terrestrial amphipods as global indicators of forest disturbance.     

An examination of scale of assessment,logging and ENSO-induced fires on butterfly diversity in Borneo

The impact of disturbance on species diversity may be related to the spatial scales over which it occurs. Here I assess the impact of logging and ENSO (El Niño Southern Oscillation) -induced burning and forest isolation on the species richness (477 species out of more than 28,000 individuals) and community composition of butterflies and butterfly guilds using small (0.9 ha) plots nested within large (450 ha) landscapes. The landscapes were located in three habitat classes: (1) continuous, unburned forest; (2) unburned isolates surrounded by burned forest; and (3) burned forest. Plots with different logging histories were sampled within the two unburned habitat classes, allowing for independent assessment of the two disturbance factors (logging and burning). Disturbance within habitat classes (logging) had a very different impact on butterfly diversity than disturbance among habitat classes (due to ENSO-induced burning and isolation). Logging increased species richness, increased evenness, and lowered dominance. Among guilds based on larval food plants, the species richness of tree and herb specialists was higher in logged areas but their abundance was lower. Both generalist species richness and abundance was higher in logged areas. Among habitat classes, species richness was lower in burned forest and isolates than continuous forest but there was no overall difference in evenness or dominance. Among guilds, generalist species richness was significantly lower in burned forest and isolates than continuous forest. Generalist abundance was also very low in the isolates. There was no difference among disturbance classes in herb specialist species richness but abundance was significantly higher in the isolates and burned forest than in continuous forest. Tree specialist species richness was lower in burned forest than continuous forest but did not differ between continuous forest and isolates.The scale of assessment proved important in estimating the impact of disturbance on species richness. Within disturbance classes, the difference in species richness between primary and logged forest was more pronounced at the smaller spatial scale. Among disturbance classes, the difference in species richness between continuous forest and isolates or burned forest was more pronounced at the larger spatial scale. The lower levels of species richness in ENSO-affected areas and at the larger (landscape) spatial scale indicate that future severe ENSO events may prove one of the most serious threats to extant biodiversity.     

Environmental stress and quantitative genetic variation in butterfly wing characteristics

Butterfly wing characteristics are extensively used as model system in studies of development, quantitative genetics and phenotypic plasticity. In spite of its evolutionary relevance, however, the effect of stress on the expression of genetic variation itself has only rarely been studied. In this paper, we explore genetic variation of wing characteristics of the Speckled wood Pararge aegeria along a host plant drought stress gradient. Forewing area, basal and distal degree of melanization and the area of five yellow wing spots were measured. We found an increase in (additive) genetic variation in degree of melanization at higher drought stress, and a similar, yet non-significant, relationship for forewing size. As a result, both the upper limits of the narrow-sense heritability and the coefficient of additive genetic variation of wing size and melanization increased with drought stress. Patterns for the different yellow wing spots were less consistent, suggesting trait-specificity in the relationships between genetic variation and environmental stress.     

Using species abundance models as indicators of habitat disturbance in tropical forests

1. In temperate communities, species abundance distributions have been used to detect ecosystem disturbance: in undisturbed habitats, distributions are claimed to generally fit log-normal models, whereas in disturbed habitats, distributions fit log-series models.
2. There is a growing literature on the effects of habitat disturbance in tropical ecosystems and several studies suggest that species abundance models may be useful in detecting disturbance, although data are lacking.
3. Nummelin (1998) claims that these models are not universal indicators of forest disturbance, but we highlight a number of problems with the data presented in Nummelin's study and conclude that it is too soon to dismiss these models. We discuss several important points arising from Nummelin's study which need to be considered if species abundance models are to be used appropriately.     

Effects of bottlenecks on quantitative genetic variation in the butterfly Bicyclus anynana

The effects of a single population bottleneck of differing severity on heritability and additive genetic variance was investigated experimentally using a butterfly. An outbred laboratory stock was used to found replicate lines with one pair, three pairs and 10 pairs of adults, as well as control lines with approximately 75 effective pairs. Heritability and additive genetic variance of eight wing pattern characters and wing size were estimated using parent-offspring covariances in the base population and in all daughter lines. Individual morphological characters and principal components of the nine characters showed a consistent pattern of treatment effects in which average heritability and additive genetic variance was lower in one pair and three pair lines than in 10 pair and control lines. Observed losses in heritability and additive genetic variance were significantly greater than predicted by the neutral additive model when calculated with coefficients of inbreeding estimated from demographic parameters alone. However, use of molecular markers revealed substantially more inbreeding, generated by increased variance in family size and background selection. Conservative interpretation of a statistical analysis incorporating this previously undetected inbreeding led to the conclusion that the response to inbreeding of the morphological traits studied showed no significant departure from the neutral additive model. This result is consistent with the evidence for minimal directional dominance for these traits. In contrast, egg hatching rate in the same experimental lines showed strong inbreeding depression, increased phenotypic variance and rapid response to selection, highly indicative of an increase in additive genetic variance due to dominance variance conversion.     

Seasonal patterns in butterfly abundance and species diversity in four tropical habitats in northern Western Ghats

In northern Western Ghats (India), four tropical habitats with different disturbance levels were monitored for diversity and seasonal patterns in butterfly communities. Species richness was highest in late monsoon and early winter. Majority of the butterfly species also showed abundance peaks in these seasons. Fire played a significant role in determining species composition in fire-afflicted areas and affected flight periods of some species but did not affect species richness. Grazing had a major impact on species composition and it favoured only those Lycaenids and Nymphalids whose caterpillars feed on herbs. In case of one of the sites where phenophases of the larval foodplant and population trend of a small Lycaenid was documented, the population showed rapid increase at the time when the plants were in suitable phenophase for growth of the caterpillars. A possible evolutionary interaction between herb-feeding and non-herb-feeding Lycaenids is proposed.     

Short-term spatial and temporal variation of sediment oxygen dynamics in a tropical tidal salt flat

Short-term spatial and temporal heterogeneity of oxygen dynamics and net primary production were studied in a tree day diurnal variation at a tidal tropical salt flat in the estuarine system of Sepetiba/Guaratiba coastal plain, Rio de Janeiro, Brazil. Oxygen concentrations were measured in situ with high temporal and spatial resolution oxygen microsensors. The results showed a remarkable heterogeneity of both oxygen penetration depth (from 0.18 to 0.85 cm) and net primary production (from −0.085 to 0.115 μmol O₂ cm⁻² s⁻¹) at different stations and sampling periods. Fast variations in abiotic factors like salinity and light due to the variable rainy weather were possibly the drivers of the high heterogeneity. In conclusion, short-term temporal changes could have a remarkable influence in sediment microalgae primary production. Not considering these changes can lead to wrong conclusions concerning the role and importance of sediment microalgae on tidal salt flats.     

Short-term variations in the abundance and cell volume of bacterioplankton in an artificial tropical lake

Circadian and spatial fluctuations in bacterioplankton abundance and cell volume were examined, for the first time, in the Municipal Lake located in the down town area of Yaoundé (Capital of Cameroon, Central Africa, ca 3° 52′ N, 11° 31′ E). Bacterial cell volumes (range, 0.05 to 0.2 μm3) were consistent with those reported for other aquatic systems while bacterial densities (0.8 to 2 × 108 cells ml-1) were among the highest values reported in pelagic systems. These variables and chlorophyll a and dissolved oxygen concentrations within a single depth-zone varied from 13 to 61%, while water temperature fluctuated only from 2 to 6%. Spatial fluctuations of physical-chemical and biological variables were generally higher during the day-time than during the night-time. A significant diel variation was provided for bacterial cell volume in the surface waters where synchronized cell division was occurring during the night. The measured bacterial abundances in this study were 4 to 17 fold higher than values known from other lakes of similar trophic status, and both cell abundance and volume were not correlated with chlorophyll. We conclude that this was due to the dependence of bacterial populations to different sources of allochthonous substrates, including untreated sewage from the major influents of the lake, resuspension of benthic material, and substrate releasing from macrophytes which are prevalent in the littoral zone of the lake. This revised version was published online in September 2006 with corrections to the Cover Date.     

Nitrogen and phosphorus additions impact arbuscular mycorrhizal abundance and molecular diversity in a tropical montane forest

Increased nitrogen (N) depositions expected in the future endanger the diversity and stability of ecosystems primarily limited by N, but also often co‐limited by other nutrients like phosphorus (P). In this context a nutrient manipulation experiment (NUMEX) was set up in a tropical montane rainforest in southern Ecuador, an area identified as biodiversity hotspot. We examined impacts of elevated N and P availability on arbuscular mycorrhizal fungi (AMF), a group of obligate biotrophic plant symbionts with an important role in soil nutrient cycles. We tested the hypothesis that increased nutrient availability will reduce AMF abundance, reduce species richness and shift the AMF community toward lineages previously shown to be favored by fertilized conditions. NUMEX was designed as a full factorial randomized block design. Soil cores were taken after 2 years of nutrient additions in plots located at 2000 m above sea level. Roots were extracted and intraradical AMF abundance determined microscopically; the AMF community was analyzed by 454‐pyrosequencing targeting the large subunit rDNA. We identified 74 operational taxonomic units (OTUs) with a large proportion of Diversisporales. N additions provoked a significant decrease in intraradical abundance, whereas AMF richness was reduced significantly by N and P additions, with the strongest effect in the combined treatment (39% fewer OTUs), mainly influencing rare species. We identified a differential effect on phylogenetic groups, with Diversisporales richness mainly reduced by N additions in contrast to Glomerales highly significantly affected solely by P. Regarding AMF community structure, we observed a compositional shift when analyzing presence/absence data following P additions. In conclusion, N and P additions in this ecosystem affect AMF abundance, but especially AMF species richness; these changes might influence plant community composition and productivity and by that various ecosystem processes.     

The impact of logging on the abundance, species richness and community composition of butterfly guilds in Borneo

Abstract:  The impact of logging on the relative abundance, species richness and community composition of four butterfly guilds (generalists, herb specialists, liana specialists and tree specialists) was assessed in differentially disturbed logging treatments located within the province of Central Kalimantan, Indonesian Borneo. Logging affected the overall butterfly composition by increasing the dominance of liana specialists at the expense of tree specialists and increasing the species richness of herb specialists and, to a lesser extent, generalists. There was no significant difference, however, in the species richness of liana specialists or tree specialists across logging treatments. The species composition of all guilds differed significantly among logging treatments with the greatest difference between unlogged forest and road sites with older and recently logged forest intermediate between these extremes. Our results indicate that logging has a disparate effect on abundance and species richness within each butterfly guild. We suggest that shifts in the dominance of butterfly guilds are due to large-scale logging-induced changes in vegetation, particularly in relation to liana abundance. The higher butterfly species richness in logged areas on the other hand is probably because of butterfly species associated with open areas entering the logged forest from roads or other large open areas.     

Land-use,environment, and their impact on butterfly populations in a mountainous pastoral landscape: species richness and family-level abundance

Extensive grasslands are considered to be of high biodiversity value, but are under threat from intensification and abandonment. We studied butterfly species richness and abundance in 47 hay and grazing meadows in the Picos de Europa, northern Spain in 2004. Nine transects were walked around the perimeter of the meadows from the 1 June to 28 July with butterflies recorded to species or species-group. Land-use, abiotic, and sward variables were also recorded. Change in meadow extent was estimated by comparing a digital map of open meadows with a cadastral map with 1950s provenance. We found: A decrease in open area, mostly attributable to reduction in grazing meadows. 75 or more butterfly species with species richness principally, and positively, influenced by altitude and presence of scrub in the body of the meadow. Hay meadow management was a positive influence on richness of satyrids. When all butterflies were considered together, the only significant factor influencing abundance was Plantago lanceolata (−ve). For sub-groups of the butterfly community there was no consistent pattern, although P. lanceolata was identified as a (−ve) factor in relation to hesperiid, nymphalid, satyrid, and Viola-feeding fritillary groups. Several regression models included components that could be linked to abiotic influences (water, aspect, altitude) but many were indicative of abandonment or relaxation of management intensity (scrub, Pteridium aquilinum, Asphodelus albus), sward components, fragmentation (distance to nearest meadow, number of meadows within 100 m), and land use (hay management, summer grazing). The results are discussed in relation to changing socio-economics, including the potential impact of tourism, and the need for financial instruments to support extensive farming.     

Land-use, environment, and their impact on butterfly populations in a mountainous pastoral landscape: individual species distribution and abundance

Butterflies were studied, at the species level, in 47 mountain meadows in a 1.5 × 1.6 km study area in the Picos de Europa National Park, Spain. Butterfly transects were carried out on nine occasions in June and July 2004 and the summed data used in binary logistic and stepwise multiple regression analyses using 28 biotic and abiotic parameters. Models were created for 37 species in total: 24 using logistic regression and 24 with multiple regression; models from both approaches were obtained for 11 species. Abiotic factors dominated many analyses with factors such as proximity to water, aspect and altitude being prominent. Abiotic factors may reflect acceptable minimum conditions for presence of a species and interact with biotic factors to determine habitat quality. Classification of the meadows as either under hay or summer grazing management, or ??winter grazing or abandoned?? was not particularly revealing probably due to inherent variability in management intensity within meadows and degree of abandonment. Features that reflected management influences, lack of management, disturbance, and sward condition featured in many analyses. Whilst many meadows are still actively managed, features that can be related to abandonment are evident for many species. The early stages of relaxation of management intensity can be positive for butterflies, but if management is not restored losses are likely as succession proceeds. The implications of this are briefly discussed.