PAST RESEARCH
Systematics of Madagascan millipede assassin bugs
Although Madagascar is one of the world's greatest biodiversity hotspots, much of its insect diversity remains unknown. One such group includes the diverse assassin bugs (Family Reduviidae). Prior to my dissertation, this was particularly true for the millipede assassin bugs (Subfamily Ectrichodiinae). Globally, this group is one of the most species-rich subfamilies of Reduviidae (>700 described species), but 10 species had only been documented from Madagascar. After examination of ~2000 specimens, it became apparent that there was a high number of undescribed species. This resulted in a large taxonomic monograph of the island's Ectrichodiinae fauna, which resulted in the description of three new genera and 63 new species. Integrative taxonomic approaches were used to revise taxa and to associate extremely dimorphic males and females.
The evolutionary and biogeographic history of the Madagascan millipede assassin bugs was also explored. This involved molecular and morphological data to infer phylogeny, divergence dating approaches, and statistical models to reconstruct ancestral biogeographic ranges. Results from this study indicate that multiple transoceanic dispersals from Oriental and Afrotropical regions are responsible for the origins of Madagascan Ectrichodiinae.
Featured publications:
Forthman, M., Weirauch, C. 2016. Phylogenetics and biogeography of the endemic Madagascan millipede assassin bugs (Heteroptera: Reduviidae: Ectrichodiinae). Mol. Phylogenet. Evol. 100: 219–233. [PDF]
Forthman, M., Chłond, D., Weirauch, C. 2016. Taxonomic monograph of the endemic millipede assassin bug fauna of Madagascar (Heteroptera: Reduviidae: Ectrichodiinae). B. Am. Mus. Nat. Hist., 400: 1–152. [Link]
Although Madagascar is one of the world's greatest biodiversity hotspots, much of its insect diversity remains unknown. One such group includes the diverse assassin bugs (Family Reduviidae). Prior to my dissertation, this was particularly true for the millipede assassin bugs (Subfamily Ectrichodiinae). Globally, this group is one of the most species-rich subfamilies of Reduviidae (>700 described species), but 10 species had only been documented from Madagascar. After examination of ~2000 specimens, it became apparent that there was a high number of undescribed species. This resulted in a large taxonomic monograph of the island's Ectrichodiinae fauna, which resulted in the description of three new genera and 63 new species. Integrative taxonomic approaches were used to revise taxa and to associate extremely dimorphic males and females.
The evolutionary and biogeographic history of the Madagascan millipede assassin bugs was also explored. This involved molecular and morphological data to infer phylogeny, divergence dating approaches, and statistical models to reconstruct ancestral biogeographic ranges. Results from this study indicate that multiple transoceanic dispersals from Oriental and Afrotropical regions are responsible for the origins of Madagascan Ectrichodiinae.
Featured publications:
Forthman, M., Weirauch, C. 2016. Phylogenetics and biogeography of the endemic Madagascan millipede assassin bugs (Heteroptera: Reduviidae: Ectrichodiinae). Mol. Phylogenet. Evol. 100: 219–233. [PDF]
Forthman, M., Chłond, D., Weirauch, C. 2016. Taxonomic monograph of the endemic millipede assassin bug fauna of Madagascar (Heteroptera: Reduviidae: Ectrichodiinae). B. Am. Mus. Nat. Hist., 400: 1–152. [Link]
Evolution of extreme sexual dimorphism in Ectrichodiinae
The evolution of sexual dimorphism in animals has long been of interest to scientists since Darwin. However, much of the scientific literature has focused on microevolutionary processes while few have reconstructed macroevolutionary patterns of extreme sexual dimorphism, especially in insects. These few studies in beetles have recovered patterns of convergent evolution for extreme sexual dimorphism, but it remains to be seen if convergent evolution of extreme sexual dimorphism occurs in other insects. To address this, I used morphological and molecular data to reconstruct the phylogeny of Ectrichodiinae, a group that exhibits a range of sexually dimorphic phenotypes — ranging from slight differences among sexes to extreme cases where association of conspecific males and females are difficult. My results showed that the last common ancestor of Ectrichodiinae exhibited limited sexual dimorphism and that extreme sexual dimorphism convergently evolved at least seven times.
Featured publication:
Forthman, M., Weirauch, C. 2017. Millipede assassins and allies (Heteroptera: Reduviidae: Ectrichodiinae, Tribelocephalinae): total evidence phylogeny, revised classification and evolution of sexual dimorphism. Syst. Entomol. 42: 575–595. [PDF]
The evolution of sexual dimorphism in animals has long been of interest to scientists since Darwin. However, much of the scientific literature has focused on microevolutionary processes while few have reconstructed macroevolutionary patterns of extreme sexual dimorphism, especially in insects. These few studies in beetles have recovered patterns of convergent evolution for extreme sexual dimorphism, but it remains to be seen if convergent evolution of extreme sexual dimorphism occurs in other insects. To address this, I used morphological and molecular data to reconstruct the phylogeny of Ectrichodiinae, a group that exhibits a range of sexually dimorphic phenotypes — ranging from slight differences among sexes to extreme cases where association of conspecific males and females are difficult. My results showed that the last common ancestor of Ectrichodiinae exhibited limited sexual dimorphism and that extreme sexual dimorphism convergently evolved at least seven times.
Featured publication:
Forthman, M., Weirauch, C. 2017. Millipede assassins and allies (Heteroptera: Reduviidae: Ectrichodiinae, Tribelocephalinae): total evidence phylogeny, revised classification and evolution of sexual dimorphism. Syst. Entomol. 42: 575–595. [PDF]
Coloration and body size correlation in Ectrichodiinae
Understanding the evolution and functions of color patterns has been a major goal of scientists since color is involved in many biotic and abiotic interactions, e.g., environmental (e.g. thermoregulation), intraspecific (e.g. sexual selection), and interspecific interactions. Cryptic coloration allows individuals to blend into the environment, but aposematic (or conspicuous warning) colors allow structurally or chemically defended individuals (or mimics of defended species) to signal distastefulness to potential predators. In some animals, aposematic colors have been shown to be positively correlated with body size. This suggests that aposematic colors are more effective in large animals. However, prior to my dissertation, the relationship between color and body size had not been supported in insects, which may have been confounded by the gregariousness of aposematic species studied. Millipede assassin bugs are an excellent model to test for this relationship given that this subfamily is comprised of species with cryptic and aposematic colors across a range of body sizes and are typically solitary as adults. I used phylogenetic comparative methods to show that aposematic coloration is positively correlated with body size and support the hypothesis that selection on body size may influence evolutionary transitions between color patterns or that selection for aposematic colors influences body size.
Featured publication:
Forthman, M., Weirauch, C. 2018. Phylogenetic comparative analysis supports aposematic colouration–body size association in millipede assassins (Hemiptera: Reduviidae: Ectrichodiinae). J. Evol. Biol., 31: 1071–1078. [PDF]
Understanding the evolution and functions of color patterns has been a major goal of scientists since color is involved in many biotic and abiotic interactions, e.g., environmental (e.g. thermoregulation), intraspecific (e.g. sexual selection), and interspecific interactions. Cryptic coloration allows individuals to blend into the environment, but aposematic (or conspicuous warning) colors allow structurally or chemically defended individuals (or mimics of defended species) to signal distastefulness to potential predators. In some animals, aposematic colors have been shown to be positively correlated with body size. This suggests that aposematic colors are more effective in large animals. However, prior to my dissertation, the relationship between color and body size had not been supported in insects, which may have been confounded by the gregariousness of aposematic species studied. Millipede assassin bugs are an excellent model to test for this relationship given that this subfamily is comprised of species with cryptic and aposematic colors across a range of body sizes and are typically solitary as adults. I used phylogenetic comparative methods to show that aposematic coloration is positively correlated with body size and support the hypothesis that selection on body size may influence evolutionary transitions between color patterns or that selection for aposematic colors influences body size.
Featured publication:
Forthman, M., Weirauch, C. 2018. Phylogenetic comparative analysis supports aposematic colouration–body size association in millipede assassins (Hemiptera: Reduviidae: Ectrichodiinae). J. Evol. Biol., 31: 1071–1078. [PDF]