Climate-land-use interactions shape tropical mountain biodiversity and ecosystem functions.

Agriculture and the exploitation of natural resources have transformed tropical mountain ecosystems across the world, and the consequences of these transformations for biodiversity and ecosystem functioning are largely unknown1-3. Conclusions that are derived from studies in non-mountainous areas are not suitable for predicting the effects of land-use changes on tropical mountains because the climatic environment rapidly changes with elevation, which may mitigate or amplify the effects of land use4,5. It is of key importance to understand how the interplay of climate and land use constrains biodiversity and ecosystem functions to determine the consequences of global change for mountain ecosystems. Here we show that the interacting effects of climate and land use reshape elevational trends in biodiversity and ecosystem functions on Africa's largest mountain, Mount Kilimanjaro (Tanzania). We find that increasing land-use intensity causes larger losses of plant and animal species richness in the arid lowlands than in humid submontane and montane zones. Increases in land-use intensity are associated with significant changes in the composition of plant, animal and microorganism communities; stronger modifications of plant and animal communities occur in arid and humid ecosystems, respectively. Temperature, precipitation and land use jointly modulate soil properties, nutrient turnover, greenhouse gas emissions, plant biomass and productivity, as well as animal interactions. Our data suggest that the response of ecosystem functions to land-use intensity depends strongly on climate; more-severe changes in ecosystem functioning occur in the arid lowlands and the cold montane zone. Interactions between climate and land use explained-on average-54% of the variation in species richness, species composition and ecosystem functions, whereas only 30% of variation was related to single drivers. Our study reveals that climate can modulate the effects of land use on biodiversity and ecosystem functioning, and points to a lowered resistance of ecosystems in climatically challenging environments to ongoing land-use changes in tropical mountainous regions.

Taxonomic revision of Plesianthidium Cameron (Apoidea: Megachilidae: Anthidiini), an endemic southern African bee genus.

The southern African bee genus Plesianthidium Cameron is revised. It comprises twelve species. Two new species are described: Plesianthidium (Spinanthidium) richtersveldense sp. nov. (Namibia and South Africa) and P. (S.) namaquaense sp. nov. (South Africa). Two species, Plesianthidium calvini (Cockerell, 1932) and P. rufocaudatum (Friese, 1909), are reinstated as valid species. Keys for the identification of the species of Plesianthidium are given.

A taxonomic revision of the southern African leaf-cutter bees, Megachile Latreille sensu stricto and Heriadopsis Cockerell (Hymenoptera: Apoidea: Megachilidae).

The five southern African subgenera of Megachile with recessed cutting edges between their teeth are revised. The entire group comprises 37 valid species, two of which are new: Megachile (Eutricharaea) gobabebensis sp. n. and Megachile (Eutricharaea) goegabensis sp. n. Other species are: Megachile (Amegachile) fimbriata Smith, Megachile (Amegachile) nasalis Smith, Megachile (Amegachile) bituberculata Ritsema, Megachile (Eutricharaea) afra Pasteels, Megachile (Eutricharaea) aurifera Cockerell, Megachile (Eutricharaea) barbata Smith, Megachile (Eutricharaea) basalis Smith, Megachile (Eutricharaea) bucephala (Fabricius), Megachile (Eutricharaea) cyanescens Friese, Megachile (Eutricharaea) eurymera Smith, Megachile (Eutricharaea) familiaris Cockerell, Megachile (Eutricharaea) konowiana Friese, Megachile (Eutricharaea) meadewaldoi Brauns, Megachile (Eutricharaea) muansae Friese, Megachile (Eutricharaea) pachyceps Friese, Megachile (Eutricharaea) regina Friese, Megachile (Eutricharaea) salsburyana Friese, Megachile (Eutricharaea) venusta Smith, Megachile (Eutricharaea) wahlbergi Friese, Megachile (Heriadopsis) whiteana Cameron, Megachile (Paracella) admixta Cockerell, Megachile (Paracella) barkeri Cockerell, Megachile (Paracella) chrysopogon Vachal, Megachile (Paracella) curtula Gerstaecker, Megachile (Paracella) edwardsi Friese, Megachile (Paracella) filicornis Friese, Megachile(Paracella) frontalis Smith, Megachile (Paracella) malangensis Friese, Megachile (Paracella) pilosella Friese, Megachile (Paracella) semierma Vachal, Megachile (Paracella) ungulata Smith, Megachile (Platysta) khamana Cockerell. Of the 78 new synonymies fimbriata vulpecula Pasteels is M. fimbriata; volkmanni ventrifasciata Strand is M. nasalis; sjoestedti var. rubripedana Strand is M. tuberculata; gratiosa Gerstaecker,concinna Smith, marusa Cameron, robertiana Cameron, venustella Cockerell, umbiloensis Cockerell and acallognatha Cockerell are M. venusta Smith; latimetatarsis Strand and rozenii Pasteels are M. basalis Smith; semifulva Friese and planatipes Cockerell are M. bucephala (Fabricius); seclusiformis Cockerell is M. salsburyana Friese; flava Friese and rhodoleucura Cockerell are M. eurymera Smith; luteola Pasteels and stellensis Pasteels are M. familiaris Cockerell; nasutula Brauns, coelostoma Cockerell, and nitidicauda Cockerell are M. barbata Smith; venustoides Strand, venustella zambesica Cockerell and pondonis Cockerell are wahlbergi Friese; okanjandica Strand and vittatula Cockerell are cyanescens Friese; leucospilura Cockerell is M. muansae Friese; cordata Smith,tardula Cameron, ekuivella Cockerell, krebsiana Strand, rhodesica Cockerell, natalica Cockerell, masaiella Cockerell, chromatica Cockerell, gratiosella Cockerell, rhodesica haematognatha Cockerell, mackieae Cockerell,flammicauda Cockerell, venusta var. semiflava Cockerell, rufulina Cockerell, rufosuffusa Cockerell, melanura Cockerell, asarna Cockerell, capiticola Cockerell, heteroscopa Cockerell, capiticola Cockerell and chrysognatha Cockerell are M. frontalis Smith; boswendica Cockerell, rubrociliata Pasteels and rufisetosa Pasteels are M. pilosella Friese; apiformis Smith is M. ungulata Smith; stellarum Cockerell, laticeps Friese, malangensis mamalapia Pasteels, obesa Pasteels and ovatomaculata Pasteels are M. malangensis Friese; flavibasis Cockerell,heterotricha Cockerell, candidicauda Cockerell, candidigena Cockerell, candidicauda spinarum Cockerell, neliCockerell, albofilosa Cockerell, discretula Cockerell, rubeola Pasteels and meesi Pasteels are M. chrysopogon Vachal; lydenburgiana Strand, aliceae Cockerell, pretoriaensis Pasteels and pycnocephala Pasteels are M. semierma Vachal; benitocola Strand and granulicauda Cockerell are M. curtula Gerstaecker; and spatulicornis Pasteels is M. edwardsi Friese. Brief descriptions are provided for all the species, as are their distributions in southern Africa, known host plants and parasites. Keys for the identification of the species are also given.

A dataset of occurrence of wild bees and their interaction with foraging plants along a livestock grazing gradient of northern Tanzania.

A dataset describing the occurrence of wild bees and their interaction with forage plants along livestock grazing gradient is critical in understanding bee-plant interaction networks and in developing conservation plans to ensure ecosystem services in human-modified landscapes. Despite this need, bee-plant datasets are scarce in Africa, and Tanzania is no exception. Therefore, in this article, we present a dataset of wild bee species richness, occurrence, and distribution collected across sites with different levels of livestock grazing intensity and forage resources thereby. The data presented in this paper supports a research article by Lasway et al., 2022 describing the effects of grazing intensity on East African bee assemblages. The paper presents primary data on bee species, collection method, date of collection, bee family, identifier, plant forage resource, forage plant life form, forage plant family, location (GPS coordinates), grazing intensity category, mean annual temperature (°C), and elevation (m asl). The data were collected intermittently between August 2018 and March 2020 from 24 study sites distributed along three levels of livestock grazing intensity with eight replicates for each: low, moderate, and high livestock grazing intensity. In each study site, two 50 × 50 m study plots were set from which bees and floral resources were sampled and quantified. The two plots were placed in a way to capture the overall structural heterogeneity of the respective habitat by placing the two plots in contrasting microhabitats where possible. For example, in moderately livestock-grazed habitats, plots were placed on sites with and without tree or shrub cover to ensure representativeness. This paper presents a dataset comprising 2,691 bee individuals from 183 species representing 55 genera of the five bee families: Halictidae (74), Apidae (63), Megachilidae (40), Andrenidae (5), and Colletidae (1). In addition, the dataset comprises 112 species of flowering plants that were identified as potential forage resources for bees. This paper supplements rare but critical data on bee pollinators in Northern Tanzania and advances our knowledge of the potential drivers of bee-pollinator whose populations diversity are declining globally. The dataset will also promote collaborations among researchers who would wish to combine and extend their data for further analysis to gain a broader understanding of the phenomenon on a larger spatial scale.

Why do leafcutter bees cut leaves? New insights into the early evolution of bees.

Stark contrasts in clade species diversity are reported across the tree of life and are especially conspicuous when observed in closely related lineages. The explanation for such disparity has often been attributed to the evolution of key innovations that facilitate colonization of new ecological niches. The factors underlying diversification in bees remain poorly explored. Bees are thought to have originated from apoid wasps during the Mid-Cretaceous, a period that coincides with the appearance of angiosperm eudicot pollen grains in the fossil record. The reliance of bees on angiosperm pollen and their fundamental role as angiosperm pollinators have contributed to the idea that both groups may have undergone simultaneous radiations. We demonstrate that one key innovation--the inclusion of foreign material in nest construction--underlies both a massive range expansion and a significant increase in the rate of diversification within the second largest bee family, Megachilidae. Basal clades within the family are restricted to deserts and exhibit plesiomorphic features rarely observed among modern bees, but prevalent among apoid wasps. Our results suggest that early bees inherited a suite of behavioural traits that acted as powerful evolutionary constraints. While the transition to pollen as a larval food source opened an enormous ecological niche for the early bees, the exploitation of this niche and the subsequent diversification of bees only became possible after bees had evolved adaptations to overcome these constraints.

Floral hosts of leaf-cutter bees (Megachilidae) in a biodiversity hotspot revealed by pollen DNA metabarcoding of historic specimens.

South Africa is a megadiverse country with three globally recognised biodiversity hotspots within its borders. Bees in particular show high diversity and endemism in the western part of the country. Not much is currently known about the floral host preferences of indigenous bees in South Africa, with data only available from observational studies. Pollen metabarcoding provides provenance information by utilising DNA analyses instead of floral visitation and traditional microscopic identification to identify pollinator food plants, which can be time consuming and imprecise. In this study, we sampled pollen from leaf-cutter bees (Megachilidae) specimens maintained in a historic insect collection (National Collection of Insects, South Africa) that were originally collected from two florally important areas in South Africa (Succulent Karoo and Savanna) and used metabarcoding to determine pollen provenance. We also sampled pollen from leafcutter bee species with wider distributions, that extend across many different biomes, to determine if these 'generalist' species show relaxed floral host specificity in some biomes. Metabarcoding involved sequencing of the nuclear internal transcribed spacer 2 (ITS2) region. Amplicons were compared to a sequence reference database to assign taxonomic classifications to family level. Sequence reads were also clustered to OTUs based on 97% sequence similarity to estimate numbers of plant species visited. We found no significant difference in the mean number of plant taxa visited in the Succulent Karoo and Savanna regions, but the widespread group visited significantly more floral hosts. Bees from the widespread group were also characterised by a significantly different composition in pollen assemblage. The time since specimens were collected did not have an effect on the mean number of taxa visited by any of the bee species studied. This study highlights national history collections as valuable sources of temporal and spatial biodiversity data.

A synopsis of the Bee occurrence data of northern Tanzania.

BACKGROUND: Bees (Hymenoptera: Apoidea: Anthophila) are the most important group of pollinators with about 20,507 known species worldwide. Despite the critical role of bees in providing pollination services, studies aiming at understanding which species are present across disturbance gradients are scarce. Limited taxononomic information for the existing and unidentified bee species in Tanzania make their conservation haphazard. Here, we present a dataset of bee species records obtained from a survey in nothern Tanzania i.e. Kilimanjaro, Arusha and Manyara regions. Our findings serve as baseline data necessary for understanding the diversity and distribution of bees in the northern parts of the country, which is a critical step in devising robust conservation and monitoring strategies for their populations. NEW INFORMATION: In this paper, we present information on 45 bee species belonging to 20 genera and four families sampled using a combination of sweep-netting and pan trap methods. Most species (27, ~ 60%) belong to the family Halictidae followed by 16 species (35.5%) from the family Apidae. Megachilidae and Andrenidae were the least represented, each with only one species (2.2%). Additional species of Apidae and Megachilidae sampled during this survey are not yet published on Global Biodiversity Information Facility (GBIF), once they will be available on GBIF, they will be published in a subsequent paper. From a total of 953 occurrences, highest numbers were recorded in Kilimanjaro Region (n = 511), followed by Arusha (n = 410) and Manyara (n = 32), but this pattern reflects the sampling efforts of the research project rather than real bias in the distributions of bee species in northern Tanzania.

Species richness is more important for ecosystem functioning than species turnover along an elevational gradient.

Many experiments have shown that biodiversity enhances ecosystem functioning. However, we have little understanding of how environmental heterogeneity shapes the effect of diversity on ecosystem functioning and to what extent this diversity effect is mediated by variation in species richness or species turnover. This knowledge is crucial to scaling up the results of experiments from local to regional scales. Here we quantify the diversity effect and its components-that is, the contributions of variation in species richness and species turnover-for 22 ecosystem functions of microorganisms, plants and animals across 13 major ecosystem types on Mt Kilimanjaro, Tanzania. Environmental heterogeneity across ecosystem types on average increased the diversity effect from explaining 49% to 72% of the variation in ecosystem functions. In contrast to our expectation, the diversity effect was more strongly mediated by variation in species richness than by species turnover. Our findings reveal that environmental heterogeneity strengthens the relationship between biodiversity and ecosystem functioning and that species richness is a stronger driver of ecosystem functioning than species turnover. Based on a broad range of taxa and ecosystem functions in a non-experimental system, these results are in line with predictions from biodiversity experiments and emphasize that conserving biodiversity is essential for maintaining ecosystem functioning.

Specialization of plant-pollinator interactions increases with temperature at Mt. Kilimanjaro.

AIM: Species differ in their degree of specialization when interacting with other species, with significant consequences for the function and robustness of ecosystems. In order to better estimate such consequences, we need to improve our understanding of the spatial patterns and drivers of specialization in interaction networks. METHODS: Here, we used the extensive environmental gradient of Mt. Kilimanjaro (Tanzania, East Africa) to study patterns and drivers of specialization, and robustness of plant-pollinator interactions against simulated species extinction with standardized sampling methods. We studied specialization, network robustness and other network indices of 67 quantitative plant-pollinator networks consisting of 268 observational hours and 4,380 plant-pollinator interactions along a 3.4 km elevational gradient. Using path analysis, we tested whether resource availability, pollinator richness, visitation rates, temperature, and/or area explain average specialization in pollinator communities. We further linked pollinator specialization to different pollinator taxa, and species traits, that is, proboscis length, body size, and species elevational ranges. RESULTS: We found that specialization decreased with increasing elevation at different levels of biological organization. Among all variables, mean annual temperature was the best predictor of average specialization in pollinator communities. Specialization differed between pollinator taxa, but was not related to pollinator traits. Network robustness against simulated species extinctions of both plants and pollinators was lowest in the most specialized interaction networks, that is, in the lowlands. CONCLUSIONS: Our study uncovers patterns in plant-pollinator specialization along elevational gradients. Mean annual temperature was closely linked to pollinator specialization. Energetic constraints, caused by short activity timeframes in cold highlands, may force ectothermic species to broaden their dietary spectrum. Alternatively or in addition, accelerated evolutionary rates might facilitate the establishment of specialization under warm climates. Despite the mechanisms behind the patterns have yet to be fully resolved, our data suggest that temperature shifts in the course of climate change may destabilize pollination networks by affecting network architecture.

Plant-pollinator interactions over time: Pollen metabarcoding from bees in a historic collection.

Pollination is a key component in agricultural food production and ecosystem maintenance, with plant-pollinator interactions an important research theme in ecological and evolutionary studies. Natural history collections provide unique access to samples collected at different spatial and temporal scales. Identification of the plant origins of pollen trapped on the bodies of pollinators in these collections provides insight into historic plant communities and pollinators' preferred floral taxa. In this study, pollen was sampled from Megachile venusta Smith bees from the National Collection of Insects, South Africa, spanning 93 years. Three barcode regions, the internal transcribed spacer 1 and 2 (ITS1 and ITS2) and ribulose-1,5-biphosphate carboxylase (rbcL), were sequenced from mixed pollen samples using a next-generation sequencing approach (MiSeq, Illumina). Sequenced reads were compared to sequence reference databases that were generated by extracting sequence and taxonomic data from GenBank. ITS1 and ITS2 were amplified successfully across all (or most) samples, while rbcL performed inconsistently. Age of sample had no impact on sequencing success. Plant classification was more informative using ITS2 than ITS1 barcode data. This study also highlights the need for comprehensive reference databases as limited local plant sequence representation in reference databases resulted in higher-level taxon classifications being more confidently interpreted. The results showed that small, insect-carried pollen samples from historic bee specimens collected from as early as 1914 can be used to obtain pollen metabarcodes. DNA metabarcoding of mixed origin pollen samples provided a faster, more accurate method of determining pollen provenance, without the need for expert palynologists. The use of historic collections to sample pollen directly from pollinators provided additional value to these collections. Sampling pollen from historic collections can potentially provide the spatial and temporal scales for investigations into changes in plant community structure or pollinator floral choice in the face of global climate change.

Changes in arthropod assemblages along a wide gradient of disturbance in Gabon.

Searching for indicator taxa representative of diverse assemblages, such as arthropods, is an important objective of many conservation studies. We evaluated the impacts of a wide gradient of disturbance in Gabon on a range of arthropod assemblages representing different feeding guilds. We examined 4 x 10(5) arthropod individuals from which 21 focal taxa were separated into 1534 morphospecies. Replication included the understory of 3 sites in each of 4 different stages of forest succession and land use (i.e., habitats) after logging (old and young forests, savanna, and gardens). We used 3 complementary sampling methods to survey sites throughout the year. Overall differences in arthropod abundance and diversity were greatest between forest and open habitats, and cleared forest invaded by savanna had the lowest abundance and diversity. The magnitude of faunal differences was much smaller between old and young forests. When considered at this local scale, anthropogenic modification of habitats did not result in a monotonous decline of diversity because many herbivore pests and their associated predators and parasitoids were abundant and diverse in gardens, where plant productivity was kept artificially high year-round through watering and crop rotation. We used a variety of response variables to measure the strength of correlations across survey locations among focal taxa. These could be ranked as follows in terms of decreasing number of significant correlations: species turnover > abundance > observed species richness > estimated species richness > percentage of site-specific species. The number of significant correlations was generally low and apparently unrelated to taxonomy or guild structure. Our results emphasize the value of reporting species turnover in conservation studies, as opposed to simply measuring species richness, and that the search for indicator taxa is elusive in the tropics. One promising alternative might be to consider "predictor sets" of a small number of taxa representative of different functional groups, as identified in our study.

Taxonomic revision of the sub-Saharan Anthidiellum Cockerell (Apoidea: Megachilidae: Anthidiini).

The Afrotropical species of the genus Anthidiellum Cockerell are revised. There are twelve species in two distinct subgenera; Pycnanthidium and Chloranthidiellum. An early record of Anthidiellum sensu stricto from Africa resulted from a misidentification. Two new species are described, Anthidiellum (Chloranthidiellum) pamae and Anthidiellum (Pycnanthidium) somaliense. Anthidiellum eritrinum is moved from the nominative subgenus to Chloranthidiellum, and a key for the identification of both sexes of the species is given. The species are redescribed with illustrations of male terminalia for most species, which have not been published before, and colour photographs. Four names are held in abeyance because their identity, and therefore status as valid species, is uncertain. They are Anthidiellum tegwaniense (Cockerell); Anthidiellum bulawayense Mavromoustakis; Anthidiellum nigripes (Friese) and Anthidiellum orichalciscopatum (Strand). They are here tentatively presumed to be junior synonyms of Anthidiellum zebra Friese.

Taxonomic revision of Cyphanthidium Pasteels (Hymenoptera: Apoidea: Megachilidae: Megachilinae: Anthidiini), an endemic Afrotropical bee genus.

The Afrotropical bee genus Cyphanthidium Pasteels is revised. It comprises four species. Cyphanthidium gessorum, new species, and Cyphanthidium whiteheadi, new species, are described as well as the previously unknown female of Cyphanthidium intermedium. A key for identifying the species is given. Supplemental information is provided on the recently published revisions of Serapista and Plesianthidium.

Taxonomic revision of the Afrotropical species of Pachyanthidium Friese (Hymenoptera: Megachilidae: Anthidiini).

The Afrotropical species of Pachyanthidium Friese are revised. Sixteen species are recognized in four subgenera. One new species, Pachyanthidium (Trichanthidium) anoplos sp. n. is described; and one species, Pachyanthidium (Trichanthidium) cucullatum (Friese), is reinstated as a valid species. Four new synonymy are proposed: Pachyanthidium minutulum Pasteels =Pachyanthidium (Trichanthidiodes) semiluteum Pasteels syn. n.; Anthidium africanum Smith = P. (P.) bicolor (Lepeletier) syn. n.; Pachyanthidium cordatum swellemdamense Mavromoustakis = Pachyanthidium (P.) cordatum (Smith) syn. n. and Anthidium cordatum var. salamense Friese 1931 = Pachyanthidium (P.) salamense (Friese 1915) syn. n. Identification keys for the Afrotropical species are given.

Taxonomic revision of the Afrotropical bee genus Serapista Cockerell (Hymenoptera: Apoidea: Megachilidae: Megachilinae: Anthidiini).

The Sub-Saharan bee genus Serapista Cockerell is revised. It comprises six species. Serapista pernigra Cockerell is restored as a valid species, S. aspernigra Eardley and Griswold, new species, is described from the eastern part of southern Africa and Serapista rhodesiana Mavromoustakis is synonymized with S. pernigra. Descriptions, keys for identification, distributional records and floral associations of the species of Serapista are given.

Predictors of elevational biodiversity gradients change from single taxa to the multi-taxa community level.

The factors determining gradients of biodiversity are a fundamental yet unresolved topic in ecology. While diversity gradients have been analysed for numerous single taxa, progress towards general explanatory models has been hampered by limitations in the phylogenetic coverage of past studies. By parallel sampling of 25 major plant and animal taxa along a 3.7 km elevational gradient on Mt. Kilimanjaro, we quantify cross-taxon consensus in diversity gradients and evaluate predictors of diversity from single taxa to a multi-taxa community level. While single taxa show complex distribution patterns and respond to different environmental factors, scaling up diversity to the community level leads to an unambiguous support for temperature as the main predictor of species richness in both plants and animals. Our findings illuminate the influence of taxonomic coverage for models of diversity gradients and point to the importance of temperature for diversification and species coexistence in plant and animal communities.