Revisions of Taxonomy

More than 50 shades of brown!

A male Bicyclus dorothea photographed in Sapo NP, Liberia

I'm currently revising the complete subtribe of Mycalesina, with the main focus on the genus Bicyclus, with the aim of producing a comprehensive book and accompanying online material to aid future identification work. The previous revision of Bicyclus made by Condamin in 1973 ended with a tally of 77 species (106 taxa if including subspecies). During my work in the field and in museum collections I have identified over 20 new species candidates in need of description. Whilst doing the revisions I am also updating the known geographic distributions, which have often been overestimated due to misidentifications.

Sex Pheromones

Rapid evolution

Sampling a male Bicyclus technatis in Afi Mountains, Nigeria

Male Bicyclus are known to produce large quantities of sex pheromones used at close range during courtship. Recently, similar pheromone systems have been documented in Heteropsis, Mycalesis and Mysodama. A large-scale sampling project I was co-leading demonstrated general patterns of Bicyclus pheromones, with the most divergent chemical blends being found in young sympatric species pairs. This suggests that these differences have evolved to avoid hybridisation. I am currently focusing on more in depth studies of pheromones and their links to other traits in several species groups of Bicyclus. I am also investigating the bigger picture by looking at pheromone use in Malagasy Heteropsis as well as amongst related Asian butterflies.

Androconia

Gain and loss of traits

Hindwing of a male Bicyclus mandanes  (Hewitson, 1873) with four androconial brushes

Males of many butterflies have androconia. These specialised wing scales are important in courtship and are therfore prime candidates for understanding the processes of speciation. Having traditionally been linked with scent communication, recent studies suggest that they also have additional, as yet unknown roles.

The subtribe Mycalesina shows an extraordinary complexity of androconia, especially in the African genus Bicyclus. Mapping these traits across more than two hundred taxa suggests that divergence in androconial number between sister species typically happened through loss. This can be deduced as androconia are often arranged as groups of functional units. The more developed structures, such as hairpencils, appear to be fully reduced almost immediately. Less conspicuous units, such as scale patches linked with these hairs, disappear more gradually leaving microscopic evolutionary fossils on the wings that help to reveal the ancestral state.

Androconia in closer detail (clockwise from top left): Mydosama mnasicles -- Mydosama anapita -- Mycalesis distanti -- Mycalesis oroatis

Male genitalia

Shapes and Functions

The male genitalia of Hallelesis halyma  (Fabricius, 1793) have large androconial brushes

The study of the male genitalia of insects has a long history in taxonomic research. It was noticed early on that these structures often looked remarkably different between species that were otherwise very similar. The traditional view explaining these differences suggested that the male and female genitalia would work as a 'Lock & Key' system making hybridisation between similar species physically impossible. Modern research has argued that other explanations might be more likely, such as increasing the mating success of individual males in species where the females mate multiple times.

Systematic studies of genitalia seeking to understand their functions have often studied groups so divergent that a single functional answer would be unlikely. In other cases, the focus has been on just a few closely related species where the differences are already known to be huge. I am therefore working in the middle ground between these two extremes by looking systematically at how the genitalia has evolved across Mycalesina butterflies as a group. Within the whole subtribe there are certain clades that show an incredible difference between sister species, other groups with a rather quick, but more gradual evolution, and finally some clades where the genitalia seem almost unchanged despite millions of years divergence between species. By correlating these patterns with those of other traits important in sexual interactions, I am searching for evidence of the ecological functions of genital structures in butterflies and other insects.

Some Mycalesina genitalia (clockwise from top left): Mydosama maianes -- Mydosama pitana -- Mycalesis suaveolens -- Mycalesis mineus

CURATORIAL WORK

Digging in the archives

The holotype of Bicyclus anisops  (Karsch, 1892)

The amount of data available in old museum collections is quite incredible. However, before this wealth of information can be used in an effective way, it is usually in need of some organisation. Over the years the rate of new acquisitions to many collections has far exceeded the rate at which they can be processed. This unfortunate situation means there can be drawers filled with unorganised and unidentified material. For anyone working on big colourful species, the level of interest received has often been high enough to ensure these groups have been kept fairly up to date. The slightly less obvious charm of Mycalesina has meant that the subtribe has often been neglected. Therefore I am working in collaboration with several major natural history collections in an effort to sort through the bulk of their available material. As part of this work I am finding new species and unexpected geographic records, which I hope will bring greater order to the group.

Clockwise from top left: The 'Amsterdam Collection' in Naturalis, Leiden -- Preparing genitalia dissections in Berlin Natural History Museum -- The African Butterfly Research Institute (ABRI) in Nairobi, Kenya -- Photographing Bicyclus at ABRI

Fieldwork

Fieldwork is absolutely vital to get fresh pheromone samples and the high quality tissues needed for more demanding modern genetic methods. I have conducted 26 expeditions to Africa to date, taking me to Ghana, Liberia, Kenya, Madagascar, Nigeria, South Africa and Uganda.

Below are a selection of photographs taken during these trips.

Clockwise from top left: Larvae of a Cymothoe butterfly (Ologbo, Nigeria) -- Funky looking mushrooms (Kibale NP, Uganda) -- Inside the highland forest (Ngel-Nyaki, Nigeria) -- Eastern black-and-white colobus (Kibale NP, Uganda)

Clockwise from top left: Termites (Jos, Nigeria) -- Tree Frog (Sapo NP, Liberia) -- Grass in flower (Jos, Nigeria) --- Twig Snake (Afi Mountians, Nigeria)

Conservation

Estimating future trends & Building local capacity

Future climate change will favour some species, while others will struggle to survive. Image shows estimated habitat suitability for two species of Bicyclus in the current climate and estimates for 2090. Warmer colours mean higher estimated suitability.

Climate change is undoubtedly one of the main threats to global biodiversity. To better understand the dynamics that define the distribution of animals I am employing climatic niche modelling on the Mycalesina system. Location records are gathered from museum collections, my own field work, and from online sources such as iNaturalist. These are then combined with climate data to produce detailed estimates of suitable habitat locations. Using data from various models of future climate change the effects of these changes on the potential range of species can then be investigated.

One key requirement for successful conservation efforts is having skilled local conservationists working actively in regions of high biodiversity. Since 2007 I have performed biomonitoring projects in tropical Africa to aid conservation NGOs and worked as a visiting lecture at A. P. Leventis Ornithological Research Institute (APLORI) in Nigeria. The institute trains Master students in conservation biology, and play an important role in shaping the future generation of conservation specialists in Africa's most populous country. APLORI is one of the organisations behind The Nigeria Bird Atlas Project (NiBAP) that have seen a large (and steadily growing) group of Nigerian citizens take to the field armed with binoculars every weekend to monitor bird populations.

Master students at the A.P. Leventis Ornithological Research Institute (APLORI) learning how to set butterfly specimens for the institute's zoological collection.

Developmental Bias

Eyespots as tools to understand evolution

Heteropsis iboina photographed in Ranomafana NP, Madagascar, showing an unusually enlarged yellow area around one of the forewing eyespots compared to the other spots.

The developmental mechanisms that generate morphology can in theory bias the independent evolution of traits sharing ontogenetic pathways, making certain evolutionary changes more likely than others. In short, developmental processes might make evolution somewhat predictable, at least in the short term.

Butterfly eyespots show strong evidence of developmental bias with colour proportions being fixed between spots, while other eyespot traits such as size, position, and number of spots seem to be independent. Current work is investigating this pattern over nearly 300 species of Mycalesina followed up by developmental manipulations to investigate how evolution have managed to release the bias between spots in some linages.

Phenotypic Plasticity

Dealing with seasonality

Wet (left) and Dry (right) season forms of Bicyclus anynana (Dry season photo by Andre Coetzer).

Many species of Mycalesina butterflies have markedly different seasonal forms. The main morphological difference is the size of the ventral eyespots that are highly reduced in the dry season. There are also further physiological changes, all tuned to maximise reproductive output in the wet season, when larval food plants are plentiful, and to increase survival in the dry season, when resources are limited. In the dry season many species stops breeding completely and the adults are generally inactive until the onset of the next rainy season. The alternating seasonal forms are mediated through developmental plasticity, so that the immature stage can develop into either phenotype to match the future adult environment.

Previous work have manly focussed on single species studies on Bicyclus anynana that have been kept as colonies in various labs around the world since 1988. My work takes a broader approach and aim to investigates the plasticity phenomenon across all species of Mycalesina. A recent paper that looked at the genus Bicyclus found a strong link between wing plasticity of mating patterns and the choice of habitats, and explored how the link had evolved.

There is a strong correlated evolutionary pattern between habitat preference and plasticity of mating strategies Bicyclus. Image from (Halali et al. 2020).