Aim Temporal dynamics of biodiversity along tropical elevational gradients are unknown. We studied seasonal changes of Lepidoptera biodiversity along the only complete forest elevational gradient in the Afrotropics. We focused on shifts of species richness patterns, seasonal turnover of communities and seasonal shifts of species’ elevational ranges, the latter often serving as an indicator of the global change effects on mountain ecosystems. Location Mount Cameroon, Cameroon. Taxon Butterflies and moths (Lepidoptera). Methods We quantitatively sampled nine groups of Lepidoptera by bait‐trapping (16,800 trap‐days) and light‐catching (126 nights) at seven elevations evenly distributed along the elevational gradient from sea level (30 m a.s.l.) to timberline (2,200 m a.s.l.). Sampling was repeated in three seasons. Results Altogether, 42,936 specimens of 1,099 species were recorded. A mid‐elevation peak of species richness was detected for all groups but Eupterotidae. This peak shifted seasonally for five groups, most of them ascending during the dry season. Seasonal shifts of species’ elevational ranges were mostly responsible for these diversity pattern shifts along elevation: we found general upward shifts in fruit‐feeding butterflies, fruit‐feeding moths and Lymantriinae from beginning to end of the dry season. Contrarily, Arctiinae shifted upwards during the wet season. The average seasonal shifts of elevational ranges often exceeded 100 m and were even several times higher for numerous species. Main conclusions We report seasonal uphill and downhill shifts of several lepidopteran groups. The reported shifts can be driven by both delay in weather seasonality and shifts in resource availability, causing phenological delay of adult hatching and/or adult migrations. Such shifts may lead to misinterpretations of diversity patterns along elevation if seasonality is ignored. More importantly, considering the surprising extent of seasonal elevational shifts of species, we encourage taking account of such natural temporal dynamics while investigating the global climate change impact on communities of Lepidoptera in tropical mountains.

Although seasonality in the tropics is often less pronounced than in temperate areas, tropical ecosystems show seasonal dynamics as well. Nevertheless, individual tropical insects’ phenological patterns are still poorly understood, especially in the Afrotropics. To fill this gap, we investigated biodiversity patterns of Lepidoptera communities at three rainforest localities in the foothills of Mount Cameroon, West Africa, one of the wettest places in the world. Our multitaxa approach covered six lepidopteran groups (fruit‐feeding butterflies and moths, the families Sphingidae, Saturniidae, and Eupterotidae, and the subfamily Arctiinae of Erebidae) with diverse life strategies. We sampled adults of the focal groups in three distinct seasons. Our sampling included standardized bait trapping (80 traps exposed for 10 days per locality and season) and attraction by light (six full nights per locality and season). Altogether, our dataset comprised 20,576 specimens belonging to 559 (morpho)species of the focal groups. The biodiversity of Lepidoptera generally increased in the high‐dry season, and either increased (fruit‐feeding moths, Arctiinae, Saturniidae) or decreased (butterflies, Sphingidae) in the transition to the wet season in particular groups. Simultaneously, we revealed a strong species turnover of fruit‐feeding Lepidoptera and Arctiinae among the seasons, indicating relatively high specialization of these communities for particular seasons. Such temporal specialization can make the local communities of butterflies and moths especially sensitive to the expected seasonal perturbations caused by the global change. Because of the key role of Lepidoptera across trophic levels, such changes in their communities could strengthen this impact on entire tropical ecosystems.

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Natural disturbances are essential for tropical forests biodiversity. In the Afrotropics, megaherbivores have played a key role before their recent decline. Contrastingly to savanna elephants, forest elephants’ impact on ecosystems remains poorly studied. Few decades ago, forests on Mount Cameroon were divided by lava flows, not being crossed by a local population of forest elephants until now. We assessed communities of trees, butterflies and two guilds of moths in the disturbed and undisturbed forests split by the longest lava flow. We surveyed 32 plots, recording 2025 trees of 97 species, and 7853 insects of 437 species. The disturbed forests differed in reduced tree density, height, and high canopy cover, and in increased DBH. Forest elephants’ selective browsing and foraging also decreased tree species richness and altered their composition. The elephant disturbance increased butterfly species richness and had various effects on species richness and composition of the insect groups. These changes were likely caused by disturbance-driven alterations of habitats and species composition of trees. Moreover, the abandonment of forests by elephants led to local declines of range-restricted butterflies. The recent declines of forest elephants across the Afrotropics probably caused similar changes in forest biodiversity and should be reflected by conservation actions.

The biodiversity of West and Central Africa is understudied, including butterflies and moths (Lepidoptera). Cameroon, through its position in between few biogeographic regions and diversity of habitats, is an important hotspot of lepidopteran diversity. However, the country also ranks low when it comes to local biodiversity knowledge. During our long-term ecological projects in the Cameroonian part of the Gulf of Guinea Highlands, we collected rich material of butterflies and moths, including a number of interesting faunistic records. In this study, we report 31 species of butterflies and moths which have not yet been recorded in Cameroon. These species comprised eight new genera records for the country. In many cases, our records represented an important extension of the species’ known distribution, including ten species whose distribution ranges extended into the Guinean biogeographic region. We also comment on the species’ elevational distribution ranges on Mount Cameroon where most of our records originated. Additionally, we confirm the presence of a butterfly Telchinia encedena, after more than a century since its first and so far its only record in Cameroon.

Mechanisms structuring tropical communities are still under-studied, especially in Afrotropical rainforests. Although insect herbivores are considered to depend on plant diversity, we hypothesized that vegetation structure, together with other microhabitat characteristics, can be more important for some insects. Here, we compared habitat associations of fruit-feeding butterflies and moths, two ecologically different groups of Lepidoptera, in three rainforest localities in foothills of Mount Cameroon, West/Central Africa. Based on a comprehensive dataset of 16,040 specimens of 398 species systematically collected by 240 traps at 48 plots (altogether 9.68 ha), we analyzed how plant community composition, habitat openness, and forest structure affect communities of butterflies and moths. We expected different habitat descriptors to predict communities of the two insect groups. Habitats of tropical fruit-feeding moth communities have never been studied before. In both analyses of species richness and community structure, butterfly communities depended mostly on forest openness. Moth species richness depended on plant diversity and forest openness, whilst the latter substantially influenced their community composition. Additionally, we revealed differences in habitat associations between understory and canopy communities of both groups. Whilst species richness of understory communities was not influenced by any habitat characteristics, it generally followed the general patterns in canopies. By contrast, composition of understory communities followed the general patterns, whilst effects of habitat characteristics on canopy communities were minor for butterflies and none for moths. The differences between such closely related groups of herbivorous insects warn against generalization based on single-taxon studies and highlight the need of communitywide research of tropical rainforests.

other field assistants for their help in the field; Štěpán Janeček, Szabolcs Sáfián, Jan E.J. 38 Mertens, Jennifer T. Kimbeng, and Pavel Potocký for help with Lepidoptera sampling at the 39 elephant-disturbed plots; Karolina Sroka, Ewelina Sroka, and Jadwiga Lorenc-Brudecka for 40 Lepidoptera setting; Elias Ndive for tree identification; Yannick Klomberg for reviewing 41 distribution of trees; Axel Hausmann for access to the Bavarian State Collection of Zoology; 42 and the Mount Cameroon National Park staff for their support.