Contrasting patterns of vertical stratification in two moth families in a Costa Rican lowland rain forest

The vertical stratification of two species-rich moth families (Lepidoptera: Arctiidae, Geometridae) was analysed in a lowland rain forest in Costa Rica. Moths were trapped with automatic 8 W ultraviolet light traps at three sites in the understorey and canopy of a primary forest at the La Selva Biological Station (10.4° N, 84.0° W). A total of 846 arctiid moths (148 species) and 946 geometrid moths (140 species) were analysed. Species richness and diversity of arctiid moths was significantly lower in the understorey than in the canopy (Fisher's alpha: 24 vs. 49) whereas geometrid moths showed an inverse pattern (Fisher's alpha: 44 vs. 27). This resulted in an overall increase in the proportion of conspicuously coloured species towards the canopy. Moth ensembles were clearly separated in multidimensional scaling ordinations, and differed significantly in their faunal composition and dominance between the strata. The available host plant data suggest that the flight height of moths was determined by larval resource availability. Examples include understorey flyers such as the geometrid genus Eois feeding on Piper, and canopy flyers such as the arctiid moth genera Aclytia, Macrocneme and Poliopastea which feed on lianas.     

Diverging diversity patterns of vascular plants and geometrid moths during forest regeneration on Mt Kilimanjaro, Tanzania

Aim This study investigates diversity patterns of vascular plants and plant‐feeding geometrid moths during montane rain forest regeneration in relation to the biogeographical and historical conditions of Mt Kilimanjaro. Location Investigations were undertaken on the south‐western slopes of Mt Kilimanjaro at altitudes between 2075 and 2265 m. Methods Thirteen plots were selected for this study. Four of these were situated in the middle of large clearings (> 1000 m²), three in secondary forest, two in mature forest remnants surrounded by secondary forest and four plots within continuous closed mature forest. Vascular plant species were recorded in an area of 20 × 20 m². Geometrid moths were attracted using lamps placed inside reflective gauze cylinders. Results Ninety‐three species of vascular plants were recorded on the plots. Plant diversity increased in the course of forest regeneration from clearings and secondary forest to mature forest remnants and mature forest. This increase was visible in all vegetation strata as well as in the species number of Dicotyledoneae. The diversity of geometrid moths conversely decreased from early to late successional stages. A total of 2276 Geometridae representing 114 morphospecies were included in the study. Local values of Fisher's α varied from 10.3 to 18.3 on clearings and in secondary forest, whereas they remained below 8.0 in mature forest and mature forest remnants. There was a significant negative correlation between the diversity of Geometridae and the number of dicots, and of plant species in the shrub layer. Main conclusions Contrary to an expected positive correlation between the diversity of vascular plants and herbivorous geometrid moths, diversity patterns of these two groups are strongly diverging due to biogeographical and ecological factors differently affecting the two groups. The increase in plant diversity can chiefly be explained with an increase in epiphyte diversity which is related to the occurrence of suitable habitats in extensive moss layers on huge Ocotea usambarensis (Engl.) trees in the mature forest. The low diversity of geometrid moths in these forests may be connected to the isolation and relatively young age of the montane rain forests on Mt Kilimanjaro. Hence only a small number of moth species adapted to the cool and perhumid conditions within moist mature forest have so far immigrated into these habitats, and time was insufficient for the evolution of many new species.     

Disturbance effects on diversity of epiphytes and moths in a montane forest in Ecuador

We sampled the diversity of epiphytes (lichens, bryophytes, vascular plants) and moths (Geometridae, Arctiidae) in mature and recovering forest and in open vegetation in the montane belt in Ecuador. No uniform pattern of change in species richness was detected among the different taxonomic groups with increasing disturbance. Species richness of epiphytic bryophytes and vascular plants declined significantly from mature forest towards open vegetation. In contrast, species richness of epiphytic lichens did not change with increasing forest alteration, while that of geometrid moths was significantly higher in recovering forest compared with mature forest and open habitats. Arctiidae were significantly more species-rich in recovering forest and open vegetation than mature forest. Hence, for some organisms, modified habitats may play an important role for biodiversity conservation in the Andes, whereas others suffer from habitat disturbance. However, trends of changes in species composition following deforestation were surprisingly concordant across most studied epiphyte and moth taxa.     

Montane Andean rain forests are a global diversity hotspot of geometrid moths

Aim Andean forests are known to be a major diversity hotspot for vascular plants and vertebrates, but virtually nothing is known about the diversity of arthropods. We examined whether montane rain forests in southern Ecuador are also a diversity hotspot for arthropods, and chose geometrid moths as a model group. Location The study area in southern Ecuador (Province Zamora‐Chinchipe, 79° W, 04° S) covers c. 40 km², with 39 collecting sites within an elevational range of 1040–2677 m a.s.l. Thirty‐five of the sites were situated in an area c. 2.5 km². Additional qualitative sampling was carried out in the same area and up to an elevation of 3100 m. Methods Nocturnal moths were collected quantitatively and qualitatively using portable light towers consisting of two 15 W fluorescent tubes, and diurnal moths were collected qualitatively using an insect net. Insects were sampled in six fieldwork periods in the years 1999–2003. As diversity measures, Fisher's alpha of the log‐series distribution as well as eight estimators of total species richness were applied. Results A total of 1266 species were recorded, 63% of which were identified to named species, whereas the remainder are likely to include many undescribed species. Quantitative samples at light towers collected 35,238 specimens representing 1223 species. The extrapolated species number for these data is 1420 (incidence coverage estimator). Twenty‐one additional nocturnal species and 22 exclusively diurnal species were sampled qualitatively at elevations between 1040 and 3100 m. The pooled value of Fisher's alpha for all quantitative samples is 246 ± 3. Main conclusions The diversity of Geometridae documented here is much higher than anywhere else in the world, even without the inclusion of additional species from adjacent lowland rain forests. The number of recorded species in this small area corresponds to more than 6% of the known world fauna of geometrid moths. Our study emphasizes the importance of protecting the remaining montane Andean rain forests. For setting priorities in conservation, more studies on insect diversity are urgently required in other regions of the Andes, since montane forests are being destroyed at an alarming rate.     

Determinants of lepidopteran community composition and species diversity in eastern deciduous forests: roles of season, eco-region and patch size

Ecologists have long recognized that factors operating at both local and regional scales influence whether a given species occurs in an ecological community. The relative roles of variables manifested at local and regional scales on community structure, however, remain an unexplored issue for many faunas. To address this question, we compared the community composition and species diversity of forest Lepidoptera between (i) large forest tracts in historically glaciated and unglaciated regions of the eastern deciduous forest in North America, and (ii) large and small forest patches within a highly fragmented forest landscape. Specifically, we used seasonally stratified sampling to test whether regional and local differences in moth communities were related to variation in stand structure and floristic composition. At the local scale, we tested three alternative hypotheses describing the effects of patch size on moth species richness: species impoverishment, species replacement, or species supplementation. Cluster analysis revealed significant compositional differences in moth communities sampled between (i) early and late seasons, (ii) glaciated and unglaciated forest eco‐regions, and (iii) large and small forest patches. Canonical correspondence analysis suggested that floristic variation at regional scales had a greater role in determining moth community composition than local vegetation or patch‐size effects. Species richness was higher in the glaciated North Central Tillplain, and was attributable to a more diverse herbaceous feeding moth assemblage. Finally, we found evidence that both species impoverishment and species replacement processes structure the moth fauna of small woodlots; the richness of moths with larvae that feed on woody plants decreased with patch area, but herbaceous feeding species increased in diversity in smaller patches. Thus, our results suggest that local and regional differences in moth community structure are mediated by differences in host‐plant resources attributable to regional biogeographic history and local differences in patch size. Because community composition appeared to be more sensitive to environmental variation than species richness, we suggest that monitoring lepidopteran species diversity in forests will not detect significant changes in species composition due to environmental change.     

Plant communities and landscape diversity along a Canadian Arctic river

Abstract. We analysed the structure and diversity of the vegetation along an Arctic river to determine the relationship between species richness and plant community structure. We examined whether variation in species richness along the corridor is structured as (1) an increase in the number of communities due to increasing landscape heterogeneity, (2) an increase in the floristic distinctiveness (β-diversity) of communities, or (3) an increase in within-community richness (α-diversity) as species-poor communities are replaced by species-rich communities. We described 24 community types and analysed the relationship between site vascular species richness (γ-diversity) and β-diversity, α-diversity, site environmental heterogeneity, and the number of distinct plant communities. We also measured diversity patterns of vascular, bryophyte, and lichen species within communities and examined their relationship to community-level estimates of environmental factors. We found that an increase in site species richness correlated with an increase in the number of communities (r²= 0.323, P= 0.0173) and β-diversity (r²= 0.388, P= 0.0075), rather than an increase in the α-diversity of individual communities. Moisture and pH controlled most of the differences in composition between communities. Measures of species richness and correlations with moisture and pH within communities differed among vascular, bryophyte, and lichen species. Bryophyte richness was positively correlated with moisture (r²= 0.862, P= 0.0010) and lichen richness was negatively correlated with moisture (r²= 0.809, P= 0.0031). Vascular plants had a peak in richness at pH 6.5 (r²= 0.214, P < 0.0001). We conclude that site variation in vascular richness in this region is controlled by landscape heterogeneity, and structured as variation in the number and distinctiveness of recognizable plant communities.     

Remote sensing improves prediction of tropical montane species diversity but performance differs among taxa

Texture information from passive remote sensing images provides surrogates for habitat structure, which is relevant for modeling biodiversity across space and time and for developing effective ecological indicators. However, the applicability of this information might differ among taxa and diversity measures. We compared the ability of indicators developed from texture analysis of remotely sensed images to predict species richness and species turnover of six taxa (trees, pyraloid moths, geometrid moths, arctiinae moths, ants, and birds) in a megadiverse Andean mountain rainforest ecosystem. Partial least-squares regression models were fitted using 12 predictors that characterize the habitat and included three topographical metrics derived from a high-resolution digital elevation model and nine texture metrics derived from very high-resolution multi-spectral orthophotos. We calculated image textures derived from mean, correlation, and entropy statistics within a relatively broad moving window (102 m × 102 m) of the near infra-red band and two vegetation indices. The model performances of species richness were taxon dependent, with the lowest predictive power for arctiinae moths (4%) and the highest for ants (78%). Topographical metrics sufficiently modeled species richness of pyraloid moths and ants, while models for species richness of trees, geometrid moths, and birds benefited from texture metrics. When more complexity was added to the model such as additional texture statistics calculated from a smaller moving window (18 m × 18 m), the predictive power for trees and birds increased significantly from 12% to 22% and 13% to 27%, respectively. Gradients of species turnover, assessed by non-metric two-dimensional scaling (NMDS) of Bray-Curtis dissimilarities, allowed the construction of models with far higher predictability than species richness across all taxonomic groups, with predictability for the first response variable of species turnover ranging from 64% (birds) to 98% (trees) of the explained change in species composition, and predictability for the second response variable of species turnover ranging from 33% (trees) to 74% (pyraloid moths). The two NMDS axes effectively separated compositional change along the elevational gradient, explained by a combination of elevation and texture metrics, from more subtle, local changes in habitat structure surrogated by varying combinations of texture metrics. The application of indicators arising from texture analysis of remote sensing images differed among taxa and diversity measures. However, these habitat indicators improved predictions of species diversity measures of most taxa, and therefore, we highly recommend their use in biodiversity research.     

Soil seed bank and floristic diversity in a forest‐grassland mosaic in southern Spain

Abstract. Soil seed bank and floristic diversity were studied in a forest of Quercus suber, a forest of Quercus canariensis and a grassland, forming a vegetation mosaic in Los Alcornocales Natural Park, southern Spain. The soil seed bank was estimated by the germination technique. In each community patch, diversity, woody species cover and herbaceous species frequency was measured. Three biodiversity components – species richness, endemism and taxonomic singularity – were considered in the vegetation and the seed bank. Forest patches had a soil seed bank of ca. 11 200–14 100 seed.m^?2 and their composition had low resemblance to (epigeal) vegetation. The grassland patch had a more dense seed bank (ca. 31 800 seed.m^?2) and a higher index of similarity with vegetation, compared with the forests nearby. The complete forest diversity was 71–78 species on 0.1 ha, including 12–15 species found only in the seed bank; the grassland species richness was higher (113 species on 0.1 ha). We discuss the role of soil seed banks in the vegetation dynamics and in the complete plant biodiversity of the mosaic landscape studied.     

Unique elevational diversity patterns of geometrid moths in an Andean montane rainforest

Alpha‐diversity of geometrid moths was investigated along an elevational gradient in a tropical montane rainforest in southern Ecuador. Diversity was measured using 1) species number, 2) extrapolated species number (Chao 1 estimator), 3) rarefied species number, and 4) Fisher's alpha. When applied to the empirical data set, 1 and 2 strongly depended on the sample size, whereas 3 and 4 were suitable and reliable measures of local diversity. At single sites, up to 292 species were observed, and extrapolation estimates range from 244 to 445 species. Values for Fisher's alpha are among the highest ever measured for this moth family, and range from 69 to 131 per site. In contrast to theoretical assumptions and empirical studies in other regions of the world, the diversity of geometrid moths remained consistently high along the entire gradient studied. Diversity measures correlated with neither altitude nor ambient temperature. The large subfamily Ennominae has previously been assumed to be a group that occurs mainly at low and medium elevations. However, no decline in diversity was found in the study area. The diversity of the other large subfamily, Larentiinae, even increased from the lowest elevations and was highest at elevations above 1800 m. The roles of a decreasing diversity of potential host‐plants, decreasing structural complexity of the vegetation, increasingly unfavourable climatic conditions and possible physiological adaptations in determining herbivore species richness are discussed. A relatively low predation pressure might be an advantage of high‐altitude habitats. The physiognomy of the Andes (folded mountains, large areas at high altitudes) might also have allowed speciation events and the development of a species‐rich high‐altitude fauna. There is evidence that the species‐richness of other groups of herbivorous insects in the same area declines as altitude increases. This emphasises difficulties that are associated with biodiversity indicator groups, and calls for caution when making generalisations from case studies.     

Plant composition and diversity in a semi-natural Mediterranean island landscape: the importance of environmental factors

Abstract

Islands crucially contribute to the Mediterranean Basin’s high floristic diversity, which, however, is at risk facing climate and land-use changes. Besides the identification of highly diverse areas, the knowledge about factors favouring diversity is of great importance. We analysed plant species diversity and composition related to environmental factors over varied vegetation units on a former Italian prison island in the northwest of Sardinia. Due to a long history of land use with grazing and later abandonment the nowadays protected island features a semi-natural landscape and can serve as an example for strongly anthropogenic altered insular ecosystems. Floristic composition, soil properties, microclimate and ungulate abundance were assessed. Relationships of vegetation composition and diversity with abiotic variables were examined by Canonical Correspondence Analysis, which indicated the importance of air temperature, soil moisture, slope gradient and C/N ratio for floristic differentiation. Most important abiotic factors for plant species richness were relative air humidity and soil moisture, while floristic diversity was mainly determined by air temperature and pH. Furthermore, observation data pointed to an adverse influence of ungulate abundance for plant species diversity. Regarding nature conservation, grazing intensity thus must be critically taken into account, especially for sensitive vegetation units like the coastal garrigue.