No abstract

No abstract

Forest fragmentation and selective logging are two main drivers of global environmental change and modify biodiversity and environmental conditions in many tropical forests. The consequences of these changes for the functioning of tropical forest ecosystems have rarely been explored in a comprehensive approach. In a Kenyan rainforest, we studied six animal-mediated ecosystem processes and recorded species richness and community composition of all animal taxa involved in these processes. We used linear models and a formal meta-analysis to test whether forest fragmentation and selective logging affected ecosystem processes and biodiversity and used structural equation models to disentangle direct from biodiversity-related indirect effects of human disturbance on multiple ecosystem processes. Fragmentation increased decomposition and reduced antbird predation, while selective logging consistently increased pollination, seed dispersal and army-ant raiding. Fragmentation modified species richness or community composition of five taxa, whereas selective logging did not affect any component of biodiversity. Changes in the abundance of functionally important species were related to lower predation by antbirds and higher decomposition rates in small forest fragments. The positive effects of selective logging on bee pollination, bird seed dispersal and army-ant raiding were direct, i.e. not related to changes in biodiversity, and were probably due to behavioural changes of these highly mobile animal taxa. We conclude that animal-mediated ecosystem processes respond in distinct ways to different types of human disturbance in Kakamega Forest. Our findings suggest that forest fragmentation affects ecosystem processes indirectly by changes in biodiversity, whereas selective logging influences processes directly by modifying local environmental conditions and resource distributions. The positive to neutral effects of selective logging on ecosystem processes show that the functionality of tropical forests can be maintained in moderately disturbed forest fragments. Conservation concepts for tropical forests should thus include not only remaining pristine forests but also functionally viable forest remnants.

We explore the potential of x-ray micro computed tomography (μCT) for the field of ant taxonomy by using it to enhance the descriptions of two remarkable new species of the ant genus Terataner: T. balrog sp. n. and T. nymeria sp. n.. We provide an illustrated worker-based species identification key for all species found on Madagascar, as well as detailed taxonomic descriptions, which include diagnoses, discussions, measurements, natural history data, high-quality montage images and distribution maps for both new species. In addition to conventional morphological examination, we have used virtual reconstructions based on volumetric μCT scanning data for the species descriptions. We also include 3D PDFs, still images of virtual reconstructions, and 3D rotation videos for both holotype workers and one paratype queen. The complete μCT datasets have been made available online (Dryad, https://datadryad.org) and represent the first cybertypes in ants (and insects). We discuss the potential of μCT scanning and critically assess the usefulness of cybertypes for ant taxonomy.

Martialinae are pale, eyeless and probably hypogaeic predatory ants. Morphological character sets suggest a close relationship to the ant subfamily Leptanillinae. Recent analyses based on molecular sequence data suggest that Martialinae are the sister group to all extant ants. However, by comparing molecular studies and different reconstruction methods, the position of Martialinae remains ambiguous. While this sister group relationship was well supported by Bayesian partitioned analyses, Maximum Likelihood approaches could not unequivocally resolve the position of Martialinae. By re-analysing a previous published molecular data set, we show that the Maximum Likelihood approach is highly appropriate to resolve deep ant relationships, especially between Leptanillinae, Martialinae and the remaining ant subfamilies. Based on improved alignments, alignment masking, and tree reconstructions with a sufficient number of bootstrap replicates, our results strongly reject a placement of Martialinae at the first split within the ant tree of life. Instead, we suggest that Leptanillinae are a sister group to all other extant ant subfamilies, whereas Martialinae branch off as a second lineage. This assumption is backed by approximately unbiased (AU) tests, additional Bayesian analyses and split networks. Our results demonstrate clear effects of improved alignment approaches, alignment masking and data partitioning. We hope that our study illustrates the importance of thorough, comprehensible phylogenetic analyses using the example of ant relationships.

BackgroundWhile thousands of ant species are arboreal, very few are able to chew and tunnel through living wood. Ants of the genus Melissotarsus (subfamily Myrmicinae) inhabit tunnel systems excavated under the bark of living trees, where they keep large numbers of symbiotic armoured scale insects (family Diaspididae). Construction of these tunnels by chewing through healthy wood requires tremendous power, but the adaptations that give Melissotarsus these abilities are unclear. Here, we investigate the morphology of the musculoskeletal system of Melissotarsus using histology, scanning electron microscopy, X-ray spectrometry, X-ray microcomputed tomography (micro-CT), and 3D modelling.ResultsBoth the head and legs of Melissotarsus workers contain novel skeletomuscular adaptations to increase their ability to tunnel through living wood. The head is greatly enlarged dorsoventrally, with large mandibular closer muscles occupying most of the dorsal half of the head cavity, while ventrally-located opener muscles are also exceptionally large. This differs from the strong closing: opening asymmetry typical of most mandibulated animals, where closing the mandibles requires more force than opening. Furthermore, the mandibles are short and cone-shaped with a wide articulatory base that concentrates the force generated by the muscles towards the tips. The increased distance between the axis of mandibular rotation and the points of muscle insertion provides a mechanical advantage that amplifies the force from the closer and opener muscles. We suggest that the uncommonly strong opening action is required to move away crushed plant tissues during tunnelling and allow a steady forward motion. X-ray spectrometry showed that the tip of the mandibles is reinforced with zinc. Workers in this genus have aberrant legs, including mid- and hindlegs with hypertrophied coxae and stout basitarsi equipped with peg-like setae, and midleg femura pointed upward and close to the body. This unusual design famously prevents them from standing and walking on a normal two-dimensional surface. We reinterpret these unique traits as modifications to brace the body during tunnelling rather than locomotion per se.ConclusionsMelissotarsus represents an extraordinary case study of how the adaptation to – and indeed engineering of – a novel ecological niche can lead to the evolutionary redesign of core biomechanical systems.Electronic supplementary materialThe online version of this article (10.1186/s12983-018-0277-6) contains supplementary material, which is available to authorized users.

This paper is a starting point towards a much needed comprehensive taxonomic treatment of the genus Pheidole in theAfrotropical region. Despite its hyperdiversity, the taxonomy of this globally distributed ant genus is limited to importantrevisions for the New World and several Asian faunas. However, Pheidole of the Afrotropical zoogeographic region hasnever been revised. The most recent Afrotropical Pheidole species descriptions are fifty years old and many are consider-ably older. Identification keys are not available and many species descriptions are of limited diagnostic value. This callsfor a series of taxonomic revisions in order to resolve the complicated taxonomic situation for the complete AfrotropicalPheidole fauna. In this paper the following preliminary morphological species groups for the Afrotropical region are de-fined: P. aurivillii group, P. excellens group, P. megacephala group, P. nigeriensis group, and P. speculifera group. We also establish and revise the P. pulchella group, which currently contains eleven species, of which seven are new. The four spe-cies described prior to this study are: P. pulchella Santschi, P. dea Santschi, P. nimba Bernard, and P. batrachorum Wheelerstat. rev., which is removed from synonymy under P. dea and regains species status. The following new synonymy isproposed (senior synonym listed first): P. pulchella Santschi = P. pulchella achantella Santschi. The following seven spe-cies are described as new: P. christinae sp. n., P. darwini, sp. n., P. glabrella sp. n., P. heliosa sp. n., P. rebeccae sp. n., P. semidea sp. n. and P. setosa, sp. n. An illustrated key combining the minor and major worker subcastes is presented.

The taxonomy of the T. bessonii, T. bonibony, T. dysalum, T. marginatum, T. tsingy, and T. weitzeckeri species groups isrevised. A total of 33 species is treated, of which 27 are newly described and one is raised to species status. The T.weitzeckeri group contains the single species T. humbloti Forel, which is of Afrotropical origin and the only representativeof the group in the Malagasy region. The species T. bessonii Forel, T. dysalum Bolton, T. marginatum Forel, and T. stein-heili Forel, which were originally members of the T. weitzeckeri group, are now placed in other groups. Tetramorium bes-sonii is the core species of the T. bessonii group, which also contains the four newly described species T. artemis sp. n., T.malagasy sp. n., T. ryanphelanae sp. n., T. wardi sp. n., and T. orientale Forel stat. n., which was a junior synonym of T.bessonii but is now raised to species rank. The T. dysalum group is a moderately-sized group with ten species, of whichonly T. dysalum and T. steinheili were previously known; the other eight species are all newly described. The newly described species in this group are: T. ambatovy sp. n., T. macki sp. n., T. mallenseana sp. n., T. orc sp. n., T. robitika sp. n.,T. sargina sp. n., T. yammer sp. n., and T. vohitra sp. n. A lectotype and several paralectotypes of T. steinheili are desig-nated. Tetramorium marginatum is the central species of the T. marginatum group, which also includes the five newly de-scribed species T. valky sp. n., T. hector sp. n., T. norvigi sp. n., T. shamshir sp. n., and T. silvicola sp. n. The T. bonibonyand T. tsingy groups represent completely new groups that consist entirely of previously unknown, undescribed species.The first group holds the new species T. bonibony sp. n., T. kali sp. n., T. sada sp. n., T. nosybe sp. n., T. olana sp. n., T.popell sp. n., and T. trafo sp. n. and T. vony sp. n. The last group, the T. tsingy group, only contains the two species T. tyrionsp. n. and T. tsingy sp. n., both among the rarest Tetramorium species in Madagascar. All groups are fully revised withillustrated species-level identification keys, and all species are described/re-described and illustrated with high qualitymontage images. In addition, the current status of the Malagasy Tetramorium species groups is discussed and further modifications are proposed.