The systematic distribution of vascular epiphytes – a critical update

Vascular epiphyte species exclusively, or at least primarily, germinate and grow on other plants without contact with the soil and, in contrast to mistletoes, without parasitizing their hosts. The last review of the systematic distribution of this diverse group of plants dates back more than two decades. The present study pursues three major goals: (1) it critically discusses conceptual problems arising from the distinction of epiphytes from non‐epiphytes; (2) it presents a compilation of epiphytic diversity derived from a vast number of sources; and (3) it arranges epiphyte diversity in an up‐to‐date taxonomic framework. The resulting compilation, which identifies 27 614 species of vascular epiphytes (including primary hemiepiphytes) representing 913 genera in 73 families, or approximately 9% of extant vascular plant diversity, is meant to be an important tool for studies on the ecology and evolution of epiphytes, but also for comparative studies with a focus on other life forms. © 2013 The Linnean Society of London     

Character divergences and convergences in canopy-dwelling Loranthaceae

The Loranthaceae is the largest plant family with aerial branch parasites termed mistletoes. Three genera of Loranthaceae are terrestrial root parasites and the remaining 72 genera are aerial parasites. Several characters, including habit, haustorial type, germination pattern, pollen morphology, chromosome number, inflorescence morphology and flower merosity, fusion, symmetry and size, are considered to reflect evolutionary relationships within the family. Convergence is a common evolutionary pattern and can confound interpretations of evolution. We investigated character evolution by mapping character states onto a phylogenetic tree based on the nuclear ITS and chloroplast trnL–trnF regions. Convergences in form were found in several characters, including habit, haustorial type, flower symmetry and merosity. These convergences typically correspond to ecological parameters such as pollination syndrome or stresses associated with the canopy habit. Other characters such as chromosome number and germination pattern illustrate divergent evolution among clades.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 150 , 101–113.     

Composition and distribution of vascular epiphytes in a tropical semideciduous forest,Ghana

The composition and distribution of vascular epiphytes were studied in two 1‐ha plots in the KNUST Botanic garden, Ghana. One‐hectare plot each was randomly set up in secondary and cultivated forests for the identification and enumeration of trees and shrubs (≥10 cm dbh), and epiphytes. Each tree was carefully examined, noting the presence, positions and life‐forms of all epiphytes. Twenty‐nine epiphyte (29) species belonging to fourteen genera and eleven families were identified in the study. These were hosted by 48 tree species and occurred in three life‐forms: hemi‐epiphytes (45%), casual epiphytes (45%) and true epiphytes (10%). The vascular epiphyte species made up 25.7% of all the identified plant species (excluding herbs and climbers) encountered. Host species (P < 0.001), habitat (P = 0.001) and their interaction (P < 0.001) had strong effects on epiphyte composition in the forests. Moraceae was the most dominant family (44.8%), while Nephrolepis undulata J. Sm. and N. biserrata (Sw.) Scott. were the commonest species of epiphytes. In terms of vertical distribution, most epiphytes were located on the trunk, while a few occurred in the canopy.     

Epiphytism,anatomy and regressive evolution in trichomanoid filmy ferns (Hymenophyllaceae)

The few studies on the evolution of epiphytism in ferns have mostly focused on xerophytic and humus‐collecting strategies, neglecting hygrophytes that are abundant in rainforests, such as the trichomanoids (Hymenophyllaceae). Using a phylogenetic approach, we studied the acquisition of epiphytism in this lineage, with the aim of identifying ecological anatomical adaptations and verifying the regressive epiphytic ‘bryophyte‐like’ strategy previously suggested for the group. Inferred evolution of anatomy and morphology, regression and ecology (more particularly colonial epiphytism) were analysed and compared using a maximum likelihood approach. Regressive evolution of anatomy and morphology is revealed in the three clades of colonial epiphytes, probably linked to the selection of water acquisition by blades rather than by regressed roots. However, the ‘bryophyte‐like’ strategy is restricted to some taxa (especially Didymoglossum). Furthermore, a relationship is revealed between large metaxylem and climbing habit. Diversification of colonial epiphytes (and some individual epiphytes) and hemi‐epiphytism would have occurred in the upper Cretaceous and Tertiary, in accordance with the timing of diversification of modern ferns and the evolution of epiphytism in other fern families in the first angiosperm‐dominated forests. This was here performed by selecting hygrophilous strategies that are unique in vascular plants. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173 , 573–593.     

The evolutionary pathway of light emission in myodocopid Ostracoda

The evolutionary history of bioluminescence and iridescence in myodocopid ostracods was estimated by phylogenetic analysis of mitochondrial 16S ribosomal RNA sequences. The inferred phylogeny of the myodocopids suggests that the common ancestor of Myodocopida evaluated in this study exhibits iridescence. This type of light emission was once lost and recaptured independently in the descendant lineages. Bioluminescent species also evolved from non-luminous ancestral species. In the suborder Myodocopina, all the bioluminescent species form a monophyletic group, suggesting that bioluminescence evolved only once. Structural differences between two bioluminescent groups in the order Myodocopida suggests independent origins for bioluminescence.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 87 , 449–455.     

Inferring evolutionary patterns from the biogeographical distributions of mutualists and exploiters

Exploitation may lead to the breakdown of obligate species-specific mutualisms. However, the mutualism between Roridula (plants) and Pameridea (hemipterans) is often exploited by spiders. The aim of the present study was to determine when the exploiters became associated with the Roridula-Pameridea mutualism. The phylogenetic and geographical associations between Roridula and Pameridea are documented and the distribution patterns of Roridula and exploiters are overlaid to see how closely they correlate. A geographical discontinuity in Roridulas ' range divides both the host plants and associated hemipterans into two sister species so that each hemipteran species is associated with a different plant species. This suggests that Roridula was associated with Pameridea before fragmentation/vicariance events split the genus, allowing allopatric speciation. By contrast, Roridula is only associated with exploiters in parts of its current range. This suggests that exploiters are unable to traverse the disjunctions in Roridulas' distribution and that they only developed associations with the mutualism after vicariance events. It is hypothesized that Pameridea and Roridula were closely associated for a long period before the invasion of nonmutualists. The absence of associated nonmutualist species may have helped facilitate the evolution of an obligate interaction between Roridula and Pameridea .  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 541–549.     

Evolution of micromorphological and chemical characters in the lichen-forming fungal family Pertusariaceae

Micromorphological characters of the fruiting bodies, such as ascus-type and hymenial amyloidity, and secondary chemistry have been widely employed as key characters in Ascomycota classification. However, the evolution of these characters has yet not been studied using molecular phylogenies. We have used a combined Bayesian and maximum likelihood based approach to trace character evolution on a tree inferred from a combined analysis of nuclear and mitochondrial ribosomal DNA sequences. The maximum likelihood aspect overcomes simplifications inherent in maximum parsimony methods, whereas the Markov chain Monte Carlo aspect renders results independent of any particular phylogenetic tree. The results indicate that the evolution of the two chemical characters is quite different, being stable once developed for the medullary lecanoric acid, whereas the cortical chlorinated xanthones appear to have been lost several times. The current ascus-types and the amyloidity of the hymenial gel in Pertusariaceae appear to have been developed within the family. The basal ascus-type of pertusarialean fungi remains unknown.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 615–626.     

How to become a yucca moth: minimal trait evolution needed to establish the obligate pollination mutualism

The origins of obligate pollination mutualisms, such as the classic yucca–yucca moth association, appear to require extensive trait evolution and specialization. To understand the extent to which traits truly evolved as part of establishing the mutualistic relationship, rather than being pre‐adaptations, we used an expanded phylogenetic estimate with improved sampling of deeply‐diverged groups to perform the first formal reconstruction of trait evolution in pollinating yucca moths and their nonpollinating relatives. Our analysis demonstrates that key life‐history traits of yucca moths, including larval feeding in the floral ovary and the associated specialized cutting ovipositor, as well as colonization of woody monocots in xeric habitats, may have been established before the obligate mutualism with yuccas. Given these pre‐existing traits, novel traits in the mutualist moths are limited to the active pollination behaviours and the tentacular appendages that facilitate pollen collection and deposition. These results suggest that a highly specialized obligate mutualism was built on the foundation of pre‐existing interactions between early Prodoxidae and their host plants, and arose with minimal trait evolution. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 847–855.     

Morphological character evolution and molecular trees in sepiids (Mollusca: Cephalopoda): is the cuttlebone a robust phylogenetic marker?

The sepiids are characterized by their cuttlebone or sepion, an internal shell resulting from secondary mineralization of a chitinous 'gladius'. The various species are identified using a combination of shell criteria and 'soft-part' characters. Using mitochondrial genes, we established phylogenetic relationships of sepiids including the three accepted genera ( Sepia , Sepiella , Metasepia ) and a species complex of uncertain status ( Doratosepion ). We showed the Sepia genus to be paraphyletic and found no direct correlation between geographical distribution and systematics. We mapped, on the molecular tree, shell characteristics commonly used as reliable diagnostic criteria for taxonomy. Due to the plasticity of the shell, these characters did not appear phylogenetically informative. In an attempt to define systematic categories related to phylogenetic relationships, new clear synapomorphies need to be established for each genus, necessitating a revision of the genus Sepia .  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 139–150.     

Molecular evidence suggests an ancient radiation for the fairy shrimp genus Streptocephalus (Branchiopoda: Anostraca)

Phylogenetic relationships among assumed Gondwanan aquatic inland invertebrate fauna are generally largely neglected, and biogeographical hypotheses for these organisms are generally inferred from historic (palaeogeographical) and contemporary distribution patterns. The distribution of the monogeneric thermophilic freshwater fairy shrimp family Streptocephalidae ( Streptocephalus ) provides a particularly useful framework to test the three contrasting biogeographical scenarios proposed for the evolution of this group: (1) the genus evolved in Laurasia and subsequently dispersed into Africa and North America; (2) the genus evolved and dispersed out of Africa and (3) the current distribution of the genus is the result of vicariance following the fragmentation of Gondwana. In the present study, the phylogenetic relationships of species in this genus are examined with the use of two mitochondrial genes (12S rRNA and COI mtDNA), while the phylogenetic relationships among the North American species and selected African taxa was investigated using the nuclear fragment (5.8S-ITS-1-18S). Phylogenetic results indicate that Streptocephalus probably evolved in Gondwana and that the current distribution patterns are a consequence of a combination of vicariance and limited dispersal. The implications for the evolution of continental freshwater crustaceans are discussed.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 313–327.