Udzungwa Mountains Research Articles

Evidence of thermophilization in Afromontane forests

Thermophilization is the directional change in species community composition towards greater relative abundances of species associated with warmer environments. This process is well-documented in temperate and Neotropical plant communities, but it is uncertain whether this phenomenon occurs elsewhere in the tropics. Here we extend the search for thermophilization to equatorial Africa, where lower tree diversity compared to other tropical forest regions and different biogeographic history could affect community responses to climate change. Using re-census data from 17 forest plots in three mountain regions of Africa, we find a consistent pattern of thermophilization in tree communities. Mean rates of thermophilization were +0.0086 °C·y−1 in the Kigezi Highlands (Uganda), +0.0032 °C·y−1 in the Virunga Mountains (Rwanda-Uganda-Democratic Republic of the Congo) and +0.0023 °C·y−1 in the Udzungwa Mountains (Tanzania). Distinct from other forests, both recruitment and mortality were important drivers of thermophilzation in the African plots. The forests studied currently act as a carbon sink, but the consequences of further thermophilization are unclear.

Discovery in leaf litter: uncovering the systematics of Porcelloderes (Heteroptera: Reduviidae: Phimophorinae)

Abstract The subfamily Phimophorinae includes ~113 species of cryptic assassin bugs found in the Neotropics and Paleotropics. Presumably due to its small size, cryptic coloration, and occurrence in the remote Eastern Arc Mountains (EAM), Porcelloderes impenetrabilis Rédei, 2012 (Heteroptera: Reduviidae: Phimophorinae), was only recently described as the first representative of this subfamily from mainland Africa. Previous morphology-based phylogenetic research on Phimophorinae (then known as Physoderinae or Epiroderinae) recovered Porcelloderes as sister taxon to the remaining epiroderine-lineage of Phimophorinae. Recent fieldwork in Tanzania has resulted in 241 additional specimens of Porcelloderes from 3 EAM) ranges. We used molecular and morphological analyses for these 241 specimens to (i) determine their species identity, (ii) test the phylogenetic position of Porcelloderes within Phimophorinae, and (iii) determine if divergence within Porcelloderes coincides with periods of climate-driven forest fragmentation in the EAM. Specimens from the Kimboza and Nguru Mountains likely represent P. impenetrabilis, but we here describe Porcelloderes harles, n. sp., from the Udzungwa Mountains. Our molecular phylogeny shows Porcelloderes nested within the epiroderine-lineage of Phimophorinae and as sister taxon to a Madagascar clade. We estimate that the epiroderine-lineage diverged from other Phimophorinae ~44 MYA. The divergence estimates for the 2 Porcelloderes species is ~15 MYA, consistent with proposed dates for other EAM assassin bugs and a period of forest fragmentation.

Archival mitogenomes identify invasion by the Batrachochytrium dendrobatidis CAPE lineage caused an African amphibian extinction in the wild.

Outbreaks of emerging infectious diseases are influenced by local biotic and abiotic factors, with host declines occurring when conditions favour the pathogen. Deterioration in the population of the micro-endemic Tanzanian Kihansi spray toad (Nectophrynoides asperginis) occurred after the construction of a hydropower dam, implicating habitat modification in this species decline. Population recovery followed habitat augmentation; however, a subsequent outbreak of chytridiomycosis caused by Batrachochytrium dendrobatidis (Bd) led to the spray toad's extinction in the wild. We show using spatiotemporal surveillance and mitogenome assembly of Bd from archived toad mortalities that the outbreak was caused by invasion of the BdCAPE lineage and not the panzootic lineage BdGPL. Molecular dating reveals an emergence of BdCAPE across southern Africa overlapping with the timing of the spray toad's extinction. That our post-outbreak surveillance of co-occurring amphibian species in the Udzungwa Mountains shows widespread infection by BdCAPE yet no signs of ill-health or decline suggests these other species can tolerate Bd when environments are stable. We conclude that, despite transient success in mitigating the impact caused by dams' construction, invasion by BdCAPE caused the ultimate die-off that led to the extinction of the Kihansi spray toad.

Dynamics of tree stems and biomass in old‐growth and secondary forests along gradients in liana dominance, elevation and soil

Abstract Lianas, or woody vines, are key components of many tropical forests and can have substantial impacts on the dynamics and functioning of these important ecosystems. Their competition with trees for resources, in particular light, can hamper the recovery of forests from disturbances. Yet, it is unclear how forest disturbance interacts with liana–tree ratio (LTR), topography and soil properties to shape tree dynamics and the trajectories of forest succession. Using temporal data from the Kilombero Valley and the Udzungwa Mountains of Tanzania, we demonstrate how the dynamics of tree stems and biomass vary between secondary and old‐growth forests with changes in the dominance of lianas and environmental gradients. Greater tree recruitment and mortality in secondary forests compared with old‐growth forests suggested rapid regeneration processes and faster turnover. However, no significant differences were found in the net annual changes in the number or biomass of trees between secondary and old‐growth forests. Our findings also showed that higher LTRs were positively associated with stem mortality but also with tree biomass growth, indicating a nuanced ecological role of lianas in forest ecosystems, which warrants further investigation to fully understand the causal factors at play. Net changes in tree stem numbers decreased significantly with elevation, implying climatic constraints on forest regeneration at higher elevations. Soil cation exchange capacity and organic carbon were found to significantly influence tree stem recruitment and net change in abundance, although their effects on biomass remained unclear. Synthesis: Our findings indicate that the recovery of tropical forests from disturbance in terms of the number and biomass of tree stems may be predictable along environmental gradients. These insights have the potential to broaden our capacity to develop more nuanced strategies that identify when and where tropical forests may require restoration interventions, with a focus on structural recovery.

Sex and size matter: Intricate dominance relationships in an East African large carnivore guild

AbstractHuman disturbance has the potential to alter competitive interactions, favoring species better able to adapt to areas used by humans. One such species is the spotted hyena (Crocuta crocuta), which has been successful in human‐dominated areas throughout Africa. In addition, hyenas are frequently successful in kleptoparasiting prey brought down by other carnivore species (e.g., leopards [Panthera pardus]). In the Udzungwa Mountains of Tanzania, leopard density declines sharply close to human settlements, and hyenas are their only competitors. Using camera trap data and a spatio‐temporal occupancy model, we assessed the relative dominance of each species through spatial co‐occurrence, altered activity patterns and temporary site avoidance. We tested the hypothesis that hyenas gain a competitive advantage over leopards in human‐dominated areas due to their relatively higher tolerance for anthropogenic activities. We found that while hyena occupancy was best predicted by prey occupancy and not strongly affected by landscape factors associated with humans, leopards, especially male leopards, were less likely to be detected close to human settlements. Female leopards, which are smaller than males, exhibited activity shifts and temporary site avoidance in response to hyenas. In response to male leopards, hyenas shifted their activity patterns to become more active around dusk and dawn. These results suggest that while hyenas may be behaviorally dominant over female leopards, they are subordinate to male leopards. We found that male leopards and hyenas were less likely to co‐occur closer to people, especially where prey was scarce, suggesting subordinance of hyenas to male leopards may be mitigated by human disturbance. Furthermore, young male leopards shifted their activity patterns to be more diurnal in response to hyena presence, suggesting that dominance relationship between hyenas and leopards develops with age and is probably related to body size. These results indicate that human disturbance has the potential to affect the competitive relationship between leopards and hyenas in the Udzungwa Mountains, but that relationships will vary with sex and body size.

A mountain of millipedes XI. The trachystreptoform spirostreptids of the Udzungwa Mountains, Tanzania (Diplopoda, Spirostreptida, Spirostreptidae)

The “trachystreptoform” species of Spirostreptidae, i.e., species which would formerly have been ascribed to the tribe Trachystreptini, from the Udzungwa Mountains are (re)described, including one new genus and five new species: Attemsostreptus reflexus Akkari & Enghoff, 2019, A. cataractae Enghoff sp. nov., A. leptoptilos Enghoff sp. nov., A. julostriatus Enghoff sp. nov., Lophostreptus tersus (Cook, 1896) (= L. ptilostreptoides Carl, 1909 syn. nov.), L. magombera Enghoff sp. nov., and Udzungwastreptus marianae Enghoff gen. et sp. nov. The type material of Lophostreptus regularis Attems, 1909 (= L. tersus) is discussed. The discussion includes paragraphs on the classification and the Udzungwa fauna of Spirostreptidae, on grouping of the Udzungwa trachystreptoform species in relation to altitude, and on the possibly recent immigration of A. reflexus and L. tersus into the Udzungwa Mts.

Gut microbiota variations in wild yellow baboons (Papio cynocephalus) are associated with sex and habitat disturbance

Although male and female mammals differ in biological traits and functional needs, the contribution of this sexual dimorphism to variations in gut bacteria and fungi (gut microbiota) in relation to habitat type has not been fully examined. To understand whether the combination of sex and habitat affects gut microbiota variation, we analyzed 40 fecal samples of wild yellow baboons (Papio cynocephalus) living in contrasting habitat types (intact, well-protected vs. fragmented, less protected forests) in the Udzungwa Mountains of Tanzania. Sex determination was performed using the marker genes SRY (Sex-determining Region Y) and DDX3X-DDX3Y (DEAD-Box Helicase 3). Samples were attributed to 34 individuals (19 females and 15 males) belonging to five social groups. Combining the results of sex determination with two amplicon sequencing datasets on bacterial (V1–V3 region of the 16S rRNA gene) and fungal (ITS2) gut communities, we found that overall, baboon females had a significantly higher gut bacterial richness compared to males. Beta diversity estimates indicated that bacterial composition was significantly different between males and females, and this was true for individuals from both well- and less protected forests. Our results highlight the combined role of sex and habitat type in shaping variation in gut microbial communities in wild non-human primates.

Tropical forest mammal occupancy and functional diversity increase with microhabitat surface area.

Many animal-environment interactions are mediated by the physical forms of the environment, especially in tropical forests, where habitats are structurally complex and highly diverse. Higher structural complexity, measured as habitat surface area, may provide increased resource availability for animals, leading to higher animal diversity. Greater habitat surface area supports increased animal diversity in other systems, such as coral reefs and forest canopies, but it is uncertain how this relationship translates to communities of highly mobile, terrestrial mammal species inhabiting forest floors. We tested the relative importance of forest floor habitat structure, encompassing vegetation and topographic structure, in determining species occupancy and functional diversity of medium to large mammals using data from a tropical forest in the Udzungwa Mountains of Tanzania. We related species occupancies and diversity obtained from a multispecies occupancy model with ground-level habitat structure measurements obtained from a novel head-mounted active remote sensing device, the Microsoft HoloLens. We found that habitat surface area was a significant predictor of mean species occupancy and had a significant positive relationship with functional dispersion. The positive relationships indicate that surface area of tropical forest floors may play an important role in promoting mammal occupancy and functional diversity at the microhabitat scale. In particular, habitat surface area had higher mean effects on occupancy for carnivorous and social species. These results support a habitat surface area-diversity relationship on tropical forest floors for mammals.

Isolating Greater Cane Rat Populations (Thryonomys swinderianus) from Eastern Arc Mountains, Tanzania: Linking Diversity to Morphometric and Molecular Characteristics

Evolutionary information on the greater cane rat (Thryonomys swinderianus) in the Eastern and Southern African regions is scarce, making population management and conservation of the species challenging. We studied T. swinderianus populations from two spatially isolated Eastern Arc Mountains in Tanzania to link molecular and geometric–morphological evidence to characterize these populations’ diversity. Fecal samples (n = 50) and skulls (n = 99) of T. swinderianus were collected from Udzungwa (north and south) and Uluguru mountains (urban and rural sites) and analyzed using molecular and geomorphometry techniques. Molecular analysis grouped the population into three distinct clades based on the location where the samples were collected, while the morphometric method was not able to distinctively separate the populations. Both methods revealed that the population obeyed the isolation by distance model with higher genetic distance between the Udzungwa and Uluguru populations and lower distance between Uluguru urban and rural populations. Both Mahalanobis and Procrustes distances in skull landmarks between the Udzungwa and Uluguru populations were significantly higher across the dorsal, ventral, and lateral views of the skulls, suggesting strongly that molecular and morphometric methods applied together can be useful in characterizing the population traits of the least known species. Our study suggests genetic and morphometric methods could complement each other in understanding the evolutionary biology and within-species diversity of vertebrate species that do not exhibit strong intra-species differentiation.

The Contribution of the Udzungwa Mountain National Park to the Livelihoods of Communities in the Morogoro Region of Tanzania

The effect of Udzungwa Mountain National Park (UMNP) on the livelihoods of communities is important.National Park is crucial in supporting the livelihoods of communities socially, economically andenvironmentally. This article analyzes the contribution and importance of the management of UMNP on thelivelihoods of communities in Kilombero District in Morogoro Region. This paper adopted mixed researchapproach where data were collected using questionnaires, interviews and observations. Data were collected inthe villages’ proximity to UMNP; Msosa, Msolwa, Mkula and Ruipa villages. A total of 233 heads of householdswere interviewed. The results showed that, heads of households were motivated to manage the park because ofthe benefits accrued from it. People managed the park because they get firewood, poles, water and othersbenefits. This paper adopted Sustainable Livelihoods Framework (SLF). SLF is a useful tool for analyzing thecontribution of UMNP to livelihood of the communities residing close to it. The livelihood supports offered byUMNP among others include income, improved food (forest vegetables), fruits and improved well-being.Challenges encountered in the management of UMNP among others include climate change, deforestation,cutting trees for building houses, wildfire, illegal collection of herbs for medicines, poaching and illegal hunting.The study concludes that, fringe communities must be motivated to manage the park because of the continuingbenefits accrued from it. The study recommends that communities should be encouraged to take measures toprotect, conserve and participate in the management of UMNP.

Climate Cycles, Habitat Stability, and Lineage Diversification in an African Biodiversity Hotspot

The Eastern Arc Mountains of Tanzania and Kenya, a montane archipelago of 13 uplifted fault blocks (sky islands) isolated by lowland arid savanna, are a center of exceptional biological endemism. Under the influence of humid winds from the Indian Ocean, forests and associated species may have persisted in this region since the final uplift of these blocks in the late Miocene. Today, these mountains are inhabited by a remarkable diversity of bird species. To better understand the evolutionary processes behind this diversity, we combined molecular phylogenetic studies of East African montane birds with paleoclimate modeling of its montane forests. Across its largest lowland barrier, the 125 km between the Usambara and Nguru/Nguu Mountains, 10 of the 14 bird lineages exhibited a phylogeographic break. Using Bayesian methods, we established that at least three periods of forest contraction and expansion affected the diversification of Eastern Arc birds. Habitat distribution models suggest that lower-elevation hills may have acted as stepping-stones connecting isolated highlands to allow for the dispersal of montane forest-dependent species across them. Periods of vicariance during paleoclimatic cycles extending back through the Last Glacial Maximum would have then isolated these populations within the highlands they had reached. The broad distribution of neoendemic species across the mountains of East Africa provides evidence of climate cycling as a driver of lineage diversification. The high incidence of narrow-range endemism of paleoendemic species on the Usambara, Uluguru, and Udzungwa Mountains of this region is harder to explain. Our paleoclimate models retrodicted the persistence of montane forest during climate cycles on several Eastern Arc sky islands but not on the Southern Tanzania Volcanic Highlands. Consistent with recent theoretical work, different rates of local extinction rather than increased rates of lineage diversification may explain the pattern of excessive narrow-range endemism on some sky islands over others. Thus, a regional filtering effect is generated, with paleoendemics maintaining populations through time only in areas where habitat persisted, providing a credible explanation for the dramatic variance in levels of endemism among different East African sky islands.

Calibrating occupancy to density estimations to assess abundance and vulnerability of a threatened primate in Tanzania

AbstractThe current decline of mammals worldwide makes quantitative population assessments crucial, especially for range‐restricted and threatened species. However, robust abundance estimations are challenging for elusive or otherwise difficult to detect species. Alternative metrics requiring only presence/absence data, that is, occupancy, are possible but calibration with independent density estimates should be foreseen, although rarely performed. Here, we calibrated density estimates from acoustic surveys to occupancy estimates from camera‐trapping detections to derive the abundance of the endangered Sanje mangabey (Cercocebus sanjei) across its entire range in the Udzungwa Mountains of Tanzania. We found marked occupancy–density relationships for the two forest blocks where this primate occurs and used them to derive spatially explicit density estimates. Occupancy increased in montane forest zones at mid‐elevation but decreased slightly with proximity to forest borders. We predicted an average density (±SE) of 0.26 ± 0.05 groups/km2in the national park and 0.24 ± 0.06 in the nature reserve. Accordingly, and given the much larger area of the reserve, the average predicted individual abundance was 1555 ± 325 and 2471 ± 571 in the national park and nature reserve, respectively. We found higher density and abundance in the nature reserve compared with previous studies. Given the past disturbance and poorer protection in the nature reserve relative to the national park, our results instill optimism for the status of the species, although occupancy analysis highlighted the potential vulnerability of this primate to human disturbance. Our approach appears valuable for spatially explicit density estimations of elusive species, and provides robust assessments of vulnerability and identification of priority areas for conservation of threatened populations.

The Significance of Motivational Incentives to the Management of Udzungwa Mountain National Park In Kilombero, Tanzania

This paper explores the significance of providing motivational incentives to local communities to attract effective management of the Udzungwa Mountain National Park (UMDP) in Kilombero district. It also examines the benefits accrued by local people from the UMDNP, explores factors motivating people to manage the UMNP, and determines challenges encountered in the management of the park. The article employs data from a study that was carried out in Msosa, Msolwa, Mkula and Ruipa villages; where a total of 233 heads of households and 7 tour guides were interviewed. The data generation process was complemented by focus group discussions and observations. The results show that active involvement of the heads of households in the management of the park was driven by benefits accrued from it. The results further suggested that local communities that live adjacent to the park are aware of the importance and role of such motivation. It is further uncovered that proper management may potentially reduce deforestation and degradation of the park. The analyst of this paper is guided by Maslow’s hierarchy of needs. The paper recommends the need for promoting the provision of motivational incentives as a useful strategy for attracting active community participation in the management of national parks.

Cryptic diversity in pygmy chameleons (Chamaeleonidae: Rhampholeon) of the Eastern Arc Mountains of Tanzania, with description of six new species

Previous molecular phylogenetic studies of pygmy chameleons have identified several cases of undescribed cryptic diversity of species, some of which have remained undescribed due to a lack of morphological information. Here, we combine descriptive morphology with principal component analysis, to quantify the overall morphological variation, and phylogenetic analysis to describe six new species of Rhampholeon from the Eastern Arc Mountains, including populations found in the Udzungwa, Rubeho, Nguru, Ukaguru, and Nguu Mountains. From our study we detected only limited morphometric variation between species. We distinguish the new species using genetics, combined with assessment of morphological features, and their geographical distribution. We highlight the threats to pygmy chameleons in East Africa from habitat change and exporting live specimens for the wildlife trade. Based on our understanding, we note a few species that we consider at risk of decline – mainly based on their narrow distribution and their apparent popularity in the export market. This study also further underlines the extraordinary biological value of the relatively small forest patches (less than 3000 km2) of the Eastern Arc, which contain more species of chameleons than any other area in mainland Africa.

Afrotropical weevils of the Cadoderus Marshall generic complex (Coleoptera: Curculionidae: Entiminae: Embrithini). Part 2. Two new species of the genus Sphrigodellus Marshall, 1942 from Udzungwa Mountains, Tanzania

Two new species of the genus Sphrigodellus Marshall, 1942 are described from cloud forests of the Udzungwa Mountains, Tanzania. Sphrigodellus griseus sp. n. from Udzungwa Scarp differs from all known species of the genus by the uniform, grey, marmorate coloration of the body, prementum with four setae, C-shaped lobes of endophallic sclerite, and extremely oblong collum of spermatheca. Sphrigodellus marshalli sp. n. is restricted to the Ukami Forest, differs from other species of the genus by the presence of black glabrous granules on the pronotum and female tergite 8 without setae on posterior margin.

A mountain of millipedes X: Species of Pyrgodesmidae and Cryptodesmidae in the Udzungwa Mountains, Tanzania (Diplopoda, Polydesmida)

Three new species of the family Pyrgodesmidae Silvestri, 1896 from the Udzungwa Mountains are described: Cryptocorypha geminiramus sp. nov., Cryptocorypha cactifer sp. nov., and Cryptocorypha exovo sp. nov. Several additional, unidentifiable pyrgodesmids from the Udzungwa Mountains are recorded. Elythesmus enghoffi Hoffman, 1978 (Cryptodesmidae Karsch, 1880), is recorded from the East Usambara (type locality), West Usambara, Uluguru, Nguru (Kanga) and Udzungwa Mountains, and its variation in size and body ring numbers is analyzed. The surface sculpture of pro- and metazonites is discussed.

Mitochondrial genetic diversity of the Greater Cane rat (Thryonomys swinderianus) populations from the Eastern Arc Mountains ecosystem, Tanzania.

Management of most herbivorous small mammal species considered to be pests in Africa is still challenging partly because of the paucity of information on their biological traits that would help to manage their destructive impacts. This gap also precludes the potential for tapping species with potential food-value to improving the economy of rural communities through, for example, sustainable game farming programs in Africa. This study investigates the genetic diversity and population demography of the African Greater Cane rat (AGC), a rodent pest of crops and game species inhabiting two isolated blocks of the Eastern Arc Mountains (EAMs), Tanzania to contribute to the species management and conservation. We used non-invasive sampling techniques and DNA sequencing of the D-loop region of MtDNA (515bp) from 46 cane rats (Thryonomys swinderianus) samples to characterize the genetic diversity and structure of the species and potential population threats faced in natural habitats. We found 25 haplotypes:15 from Uluguru and 9 from Udzungwa mountains populations, containing 49 polymorphic regions (32 parsimoniously informative and 17 singleton sites). Haplotype diversity (range: 0.849-0.995) did not differ substantially across populations but the median haplotype diversity for Udzungwa South was overall lower than for other populations. Nucleotide diversity averaged 0.00641, 0.01528, 0.0111 and 0.01313, respectively for Udzungwa South, Udzungwa North, Uluguru Rural and Uluguru Urban, suggesting high genetic diversity within the four populations. Analysis of molecular variance (AMOVA) indicated significantly high genetic differences between the four populations (FST = 0.16, p = 0.00098) whereas neutrality test (FU's Fs) values were negative, indicating historical population expansion. Similarly, the Bayesian skyline analysis indicated a recent demographic expansion suggesting limited bottlenecks in the recent past in this population. Our results show the AGC population in EAMs consists of four distinct populations which have experienced a recent population expansion, especially among the urban population due perhaps to influence of urbanization process that may have favored assisted species movements across the rural-urban landscapes. Future research should focus on understanding impact of geographical isolation on the genetic structure and diversity of this species.

Phylogenetic relationships, distribution and abundance of Charaxes mtuiae Collins Congdon and Bampton, 2017 (Papilionoidea: Nymphalidae: Charaxinae) and its host plant in the Udzungwa mountain forest in southern Tanzania

Charaxes mtuiae Collins Congdon and Bampton, 2017 was discovered in 2005 in the Udzungwa Mountains of Tanzania, where the caterpillars feed exclusively on Diospyros natalensis. This study was aimed at determining the abundance and spatial distribution of C. mtuiae and its host plant, as well as its evolutionary history. Field surveys were conducted between April 2017 and December 2018. Stems of the host plant were counted in sampling plots and their diameter at breast height measured, and categorised as mature if the diameter was ≥ 12 cm, otherwise as recruits. Charaxes mtuiae was sampled by searching for immatures on the leaves of the host plant and capturing adults using traps. DNA material of C. mtuiae was extracted, sequenced, and aligned with 63 other species of Charaxes. A total of 1,173 stems of the host plant including 1,064 recruits and 102 mature stems were recorded. One specimen of C. mtuiae found at caterpillar stage was raised to adulthood, and three empty pupa cases of C. mtuiae were recorded. The phylogenetic relationship of C. mtuiae and its sister lineages was concordant with previous descriptions, based on morphology. Our results indicate that C. mtuiae is rare, despite the high abundance of its host plant. Continued research and monitoring of C. mtuiae population to understand its ecological requirements; and expansion of surveys into other parts of the country where the host plant occurs to establish its distribution country-wide are recommended.

Seasonal Changes in an Afromontane Forest Bird Community in Tanzania

Seasonal variation in the composition of avian communities is poorly documented in African montane forests. Using field observations, mist-netting data (63,424 NMH), recording of mixed-species flocks (160 flocks noted), and of the feeding ecology of greenbuls (757 observations), we document marked seasonal changes in a bird community in an East African montane forest (1,340–2,130 m) in the Udzungwa Mountains in south-central Tanzania. This mountain range contains the largest remaining forests in the Eastern Arc Mountains in Tanzania, part of a key global biodiversity hotspot. Our analysis is based on data in the dry and wet season from about 12 months of fieldwork. Field observation data combined with mist-net data demonstrate noticeable seasonal changes in certain species’ abundances, indicating (i) seasonal movements out of the montane forest during the dry season and (ii) movements of part of the populations for other species. Our mist-net results show a significant difference in species abundances between the two seasons driven by 16 species. We also document significant changes in diet for two species of greenbuls, which shift feeding behavior from arthropods in the wet season to include a larger proportion of fruit in their dry season diet. Our results further show that birds are more active in mixed-species flocks in the dry season, with a significantly higher average number of species and of individuals in the dry season, i.e., 11.3 (±0.52 SE) species, 32.3 (±1.76 SE) individuals] compared to the wet season 9.7 (±0.78 SE) species, 20.8 (±1.85 SE) individuals]. One of two very distinctive types of mixed-species flocks – confined to the understory – exists only in the dry season. We discuss these changes to seasonal variability in climate, i.e., temperature and precipitation.

Ant Diversity Declines with Increasing Elevation along the Udzungwa Mountains, Tanzania

Biodiversity patterns along elevational gradients are generally characterised by monotonic decreases or mid-elevational peaks in species richness, while elevational zones may be characterised by distinct assemblages, or higher zones may be subsets of lowland assemblages. Elevational gradients in diversity have been less studied in the Afrotropical region. This study documents ant diversity patterns in three forest types associated with the tropical mountains of Udzungwa; we hypothesise that: (1) ant diversity and activity will show a monotonic decrease from mid-elevation with increasing elevation and (2) that forests associated with different elevations will have a distinct ant assemblage. Pitfall traps were deployed at three targeted elevations (650–800, 800–1400, and 1400–1500 m a.s.l.). Ant species richness declined with increasing elevation from 650 m a.s.l. and formed three elevational assemblages with lower elevation forests having almost twice as many species as sub-montane forests and three times as many as that of the montane forests. In contrast, overall ant activity peaked at 800–1400 m a.s.l. The ant assemblages associated with the lower elevation forest were very distinct, while assemblages associated with the sub-montane and montane forests shared species. Our study reveals valuable and relevant information for biodiversity monitoring and conservation planning as the species associated with each forest type may be used as indicator species for assessing biodiversity responses to climate change and anthropogenic activities on these mountains.