Longitudinal river zonation in the tropics: examples of fish and caddisflies from the endorheic Awash River, Ethiopia

Specific concepts of fluvial ecology are well studied in riverine ecosystems of the temperate zone but poorly investigated in the Afrotropical region. Hence, we examined the longitudinal zonation of fish and adult caddisfly (Trichoptera) assemblages in the endorheic Awash River (1,250 km in length), Ethiopia. We expected that species assemblages are structured along environmental gradients, reflecting the pattern of large-scale freshwater ecoregions. We applied multivariate statistical methods to test for differences in spatial species assemblage structure and identified characteristic taxa of the observed biocoenoses by indicator species analyses. Fish and caddisfly assemblages were clustered into highland and lowland communities, following the freshwater ecoregions, but separated by an ecotone with highest biodiversity. Moreover, the caddisfly results suggest separating the heterogeneous highlands into a forested and a deforested zone. Surprisingly, the Awash drainage is rather species-poor: only 11 fish (1 endemic, 2 introduced) and 28 caddisfly species (8 new records for Ethiopia) were recorded from the mainstem and its major tributaries. Nevertheless, specialized species characterize the highland forests, whereas the lowlands primarily host geographically widely distributed species. This study showed that a combined approach of fish and caddisflies is a suitable method for assessing regional characteristics of fluvial ecosystems in the tropics.

Carcass consumption by Nasutitermes callimorphus (Blattodea: Isoptera) in highland forests from Brazil

This note reports the occurrence of carcass feeding by Nasutitermes callimorphus, a endemic termite from brazilian evergreen forests. Based on this observation and previous reports, it is plausible to think that drought may play a important role in the occurrence of necrophagy in termites.

BULBOPHYLLUM ACEHENSE (ORCHIDACEAE), A NEW SPECIES OF SECTION BECCARIANA FROM ACEH, SUMATRA, INDONESIA

Sumatra island has been considered as one of the diversity centers for Bulbophyllum species in Indonesia. During botanical exploration held in the mid of 2019, specimens of the genus Bulbophyllum (Orchidaceae) section Beccariana have been collected from highland forests in Aceh Province, Sumatra, Indonesia. Their flower morphology and plant habitus are relatively close to Bulbophyllum cornutum (Blume) Rchb.f. (section Beccariana). Therefore, the aim of this research is to compare the Bulbophyllum sp. from Aceh with closely resemble species in section Beccariana, also to describe and illustrate the morphological characteristics of this Bulbophyllum species from Aceh. Morphological description was carried out by characterizing the flowers and plant habit of the living plants, spirit materials, dried herbarium specimens and photographs. Morphological comparisons with other closely resemble Bulbophyllum species were carried out based on data from protologue, living plants, herbarium specimens and several taxonomic references. The result based on morphological comparisons has showed there were several distinct differences on their flower characteristics, especially on the labellum. Therefore, this Bulbophyllum sp. from Aceh is here described and illustrated as new species, namely Bulbophyllum acehense.Keywords: Bulbophyllum, Sumatra, Orchidaceae

Influence of phylogenetic structure and climate gradients on geographical variation in the morphology of Mexican flycatcher forests assemblages (Aves: Tyrannidae)

Morphological variation is strongly related to variation in the ecological characteristics and evolutionary history of each taxon. To explore how geographical variation in morphology is related to different climatic gradients and phylogenetic structure, we analyzed the variation of morphological traits (body size, bill, and wing) of 64 species of tyrant flycatchers (Tyrannidae) distributed in Mexico. We measured these morphological traits in specimens from biological collections and related them to the climatic and topographic data of each collection locality. We performed the analyses separately at two levels: (1) the regional level and (2) the assemblage level, which was split into (assemblage I) lowland forests and (assemblage II) highland forests and other vegetation types. We also calculated the phylogenetic structure of flycatchers of each locality in order to explore the influence of climatic variables and the phylogenetic structure on the morphological variation of tyrant flycatchers, by means of linear mixed-effects models. We mapped the spatial variation of the relationship between morphological traits and environmental gradients, taking into account the phylogenetic structure. Important climatic variables explaining the morphological variation were those of temperature ranges (seasonality) and the results suggest that the phylogenetic clustering increases towards the highlands of Sierra Madre Oriental and Sierra Madre del Sur, and the lowlands of Balsas Depression. For the regional level, the spatial distribution of body size showed a pattern coincident with Bergmann’s rule, with increasing in size from south to north. In the tropical lowland forests assemblage, body size tend to increase in seasonally dry forests (western Mexico) and decrease in the humid ones (eastern Mexico). In the assemblage of highland forests and other types of vegetation, morphological trait values increased northeast to southwest. Phylogenetic structure helped to explain the variation of morphology at the assemblage level but not at the regional level. The patterns of trait variation in the lowland and highland assemblages suggest that parts of morphological variation are explained both by the climatic gradients and by the lineage relatedness of communities. Overall, our results suggest that morphological variation is best explained by a varied set of variables, and that regression models representing this variation, as well as integrating phylogenetic patterns at different community levels, provide a new understanding of the mechanisms underlying the links among biodiversity, its geographical setting, and environmental change.

New species, diversity, systematics, and conservation assessment of the Puppet Toads of Sumatra (Anura: Bufonidae: Sigalegalephrynus)

Using a combination of morphological and molecular data we recognize three new species of Puppet Toad, Sigalegalephrynus Smart, Sarker, Arifin, Harvey, Sidik, Hamidy, Kurniawan & Smith, a recently described genus endemic to the highland forests of Sumatra, Indonesia. Phylogenetic analysis of mitochondrial DNA sequences recovered a monophyletic relationship among all Puppet Toads, with two distinct evolutionary clades, a northern and a southern. The northern clade includes Sigalegalephrynus gayoluesensis sp. nov., and S. burnitelongensis sp. nov., and the southern clade includes S. harveyi sp. nov., S. mandailinguensis, and S. minangkabauensis. With the discovery of these three new species, Sigalegalephrynus contains more endemic species than any other genus of toad in Indonesia. We used maximum entropy, implemented in MaxEnt, to identify suitable habitats and occurrence probability of additional undescribed new species from the island. The most important predictors of Sigalegalephrynus distribution were elevation (64.5%) and land cover (7.11%). Based on the probability of presence, it is likely that there are many more species of the genus awaiting discovery in Sumatra. Our analysis, based on IUCN Red List of Threatened Species category and criteria, shows that all of the five species of Sigalegalephrynus are in great risk of extinction and should be placed into the Endangered (EN) category of IUCN Red List.

Lack of negative density-dependence regulation in a dominant oak tree from a neotropical highland forest

Conspecific negative density-dependence(CNDD) is one of the main mechanisms proposed to regulate species coexistence. Tropical highland forests, in contrast to diverse lowland forests, are commonly dominated by a few tree species. Testing the importance of density-dependence effects on seedling establishment of dominant trees may provide insights on the mechanisms regulating population dynamics and forest composition of tropical highlands. We tested the importance of CNDD regulation on seedling survival and recruitment ofQuercus costaricensis, a monodominant oak in the Talamanca highland forests of Costa Rica. We used spatial statistics and generalized linear mixed models to test the effects of conspecific density, distance to the nearest adult, density ofChusqueabamboo shoots, and herbivory on the annual survival probability of 3538 seedlings between 2014 and 2017. We did not find any effect of CNDD on seedling survival. However, bamboo density and herbivory both significantly decreased seedling survival. All seedlings had signs of herbivory and predator satiation may explain the lack of density dependent regulation in this species. We argue that the lack of intraspecific density regulation at the seedling stage may explain the dominance ofQ. costaricensisin the highland forests of Costa Rica. Local density of this endemic oak is instead regulated by herbivory and the density ofChusquea.