A transcontinental comparison of the diversity and composition of tropical forest understory herb assemblages

Although tropical forests are renowned for their high plant diversity, to date there has been no global quantitative evaluation of the local species richness of terrestrial forest herbs in tropical forests. In this paper, richness and composition of terrestrial herb assemblages is compared in tropical forests of America, Africa and South East Asia. We established 86 non-continuous transects of 445m each. Herb species richness was analysed and compared to six environmental parameters using minimal adequate regression models and simultaneous autoregressive models. At the global scale, we found a close relationship between herb species richness and temperature parameters, with no differences between continents. The subdivision into three main taxonomic groups (ferns, monocots, dicots) showed that each group has distinct relations to environmental factors and differences in richness between continents. Most of the 72 families found have pantropical distributions but 12, 11, and 16 families were significantly over-represented in America, Africa, and Asia, respectively. Although total species richness was closely related to climatic factors, ferns, monocots and dicots were represented by distinct sets of families with varying species richness on each continent. Which species are found at a given site may thus reflect group-specific evolutionary and historical factor

First record of bat-pollination in the species-rich genus Tillandsia (Bromeliaceae)

Background and Aims Bromeliaceae is a species-rich neotropical plant family that uses a variety of pollinators, principally vertebrates. Tillandsia is the most diverse genus, and includes more than one-third of all bromeliad species. Within this genus, the majority of species rely on diurnal pollination by hummingbirds; however, the flowers of some Tillandsia species show some characteristics typical for pollination by nocturnal animals, particularly bats and moths. In this study an examination is made of the floral and reproductive biology of the epiphytic bromeliad Tillandsia macropetala in a fragment of humid montane forest in central Veracruz, Mexico. Methods The reproductive system of the species, duration of anthesis, production of nectar and floral scent, as well as diurnal and nocturnal floral visitors and their effectiveness in pollination were determined. Key Results Tillandsia macropetala is a self-compatible species that achieves a higher fruit production through outcrossing. Nectar production is restricted to the night, and only nocturnal visits result in the development of fruits. The most frequent visitor (75 % of visits) and the only pollinator of this bromeliad (in 96 % of visits) was the nectarivorous bat Anoura geoffroyi (Phyllostomidae: Glossophaginae). Conclusions This is the first report of chiropterophily within the genus Tillandsia. The results on the pollination biology of this bromeliad suggest an ongoing evolutionary switch from pollination by birds or moths to bat

Biological variation in climbing aroids

Antecedentes y Objetivos: Las especies de Araceae son conocidas por sus distintas formas de vida; sin embargo, la terminología relacionada con este grupo genera confusiones conceptuales dentro de la comunidad científica. Nuestro objetivo fue demostrar la confusión conceptual actual derivada de la literatura y ejemplares de herbario vs. observaciones y datos de campo. Métodos: Se realizó una revisión exhaustiva de fuentes de información relevantes sobre las formas de vida de aráceas, incluyendo floras y tratamientos taxonómicos, así como de ejemplares de herbario. Adicionalmente, se llevó a cabo un censo de seis especies de aráceas en la Estación de Biología Tropical “Los Tuxtlas”, Veracruz, México. Para cada individuo se buscaron las conexiones de sus raíces adventicias y tallos con el suelo, además se tomaron medidas de su longitud total y hojas para crear tres clases ontogénicas. Resultados clave: Se presentan las descripciones de formas de vida de 30 especies de Araceae trepadoras de Veracruz publicadas en nueve publicaciones, mostrando una marcada inconsistencia en el uso de la terminología. El análisis de los datos documentados en los ejemplares de herbario reveló para 17 especies, que todas fueron asignadas con al menos tres de ocho diferentes categorías de hábito, principalmente como epífita, hemiepífita y trepadora. De las seis especies censadas en campo, la mayoría de los individuos tiene conexión con el suelo. Conclusiones: Las asignaciones de formas de vida basadas en observaciones de campo sin tener datos cuantitativos sobre el contacto de las plantas con el suelo son problemáticas. Más bien, es necesario analizar y aclarar la ontogenia de las aráceas trepadoras, lo que puede contribuir a estructurar adecuadamente nuestros conceptos y evitar ambigüedades en la terminología. Asimismo, también se debería evitar que se agrupen a las especies de Araceae indistintamente en estudios sobre epífitas, lo cual lleva a sobreestimar la riqueza reportada.Background and Aims: The species of Araceae are known for their diversity of life forms; however, the terminology regarding this group generates conceptual confusion within the scientific community. Our objective was to demonstrate the current conceptual confusion based on the literature, herbarium vouchers vs. observations and field data. Methods: A thorough review of relevant sources of information on aroid life forms was carried out, including floras and taxonomic treatments, as well as herbarium vouchers. Additionally, a census of six aroid species was conducted at the Tropical Biological Station “Los Tuxtlas”, Veracruz, Mexico. For each individual we searched for the connections of its adventitious roots and stems with the soil, in addition we took measurements of its total length and leaves to create three ontogenic classes. Key results: We present descriptions of life forms of 30 species of climbing Araceae from Veracruz published in nine publications, showing pronounced inconsistency in the use of terminology. The analysis of the data documented in the herbarium specimens revealed for 17 species, that these were assigned to at least three of eight different habit categories, mainly as epiphyte, hemiepiphyte and climber. Of the six species surveyed in the field, most of the individuals have a connection with the soil. Conclusions: Life form assignments based on field observations without quantitative data on the contact of plants with the soil are problematic. Rather, it is necessary to analyze and clarify the ontogeny of climbing aroids, which can help to properly structure our concepts and avoid ambiguities in terminology. Likewise, it should also be avoided that Araceae species are lumped indiscriminately in epiphyte studies, which leads to an overestimation of the reported richness

The role of hummingbirds in the evolution and diversification of Bromeliaceae: unsupported claims and untested hypotheses

At least half of the 3600 species of Bromeliaceae are pollinated by hummingbirds. There is little doubt that the four to 12 evolutionary shifts towards and c. 32 shifts away from hummingbird pollination opened new evolutionary spaces for bromeliad diversification, and that hummingbird pollination has led to increased bromeliad diversification rates. However, the mechanisms leading to these increased rates remain unclear. We here propose that there are four main types of mechanisms that may increase diversification rates of hummingbird-pollinated bromeliad clades: (1) bromeliad speciation through adaptation to different hummingbird species; (2) increased allopatric speciation in hummingbird-pollinated clades due to lower pollen transfer efficiency compared with other pollinators; (3) differential speciation rates in hummingbird-pollinated clades dependent on of flowering phenology and hummingbird behaviour; and (4) higher speciation rates of bromeliads in montane environments (where hummingbird pollination predominates) due to topographic population fragmentation. To date, none of these hypotheses has been appropriately tested, partly due to a lack of data, but also because research so far has focused on documenting the pattern of increased diversification in hummingbird-pollinated clades, implicitly assuming that this pattern supports an underlying mechanism while ignoring the fact that several competing mechanisms may be considered. The aim of the present review is to increase awareness of these mechanisms and to trigger research aimed at specifically testing them. We conclude that much additional research on the roles of hummingbird behaviour and gene flow between bromeliad species is needed to elucidate their contribution to the evolution of diversity in bromeliads and other plant families

Lepidopteran visitors of Anthurium inflorescences

International audienc

Monstera florescanoana (Araceae), a new species from central Veracruz, Mexico Monstera florescanoana (Araceae), una especie nueva de la región central de Veracruz, México

Monstera florescanoana (Araceae), a new species in section Monstera, endemic to central Veracruz, Mexico, is described and illustrated. This species appears to be most closely related to Monstera siltepecana Matuda and Monstera dubia (Kunth) Engl. et K. Krause.Se describe e ilustra Monstera florescanoana (Araceae), una nueva especie de la sección Monstera, endémica de la región central del estado de Veracruz, México. Esta especie parece estar más cercanamente relacionada a los taxones Monstera siltepecana Matuda y Monstera dubia (Kunth) Engl. et K. Krause

Effects of altitude and climate in determining elevational plant species richness patterns: a case study from Los Tuxtlas, Mexico

Altitudinal changes of composition and richness of montane plant assemblages are complex, depending on the taxonomic group and gradient conditions, with different factors involved that are directly altitude-dependent (e.g., temperatures, air pressure) and altitude-independent (e.g., precipitation, cloud cover, area). In order to assess the relative impacts of temperature, precipitation, air humidity, and area of altitudinal belts on plant diversity, we analyzed diversity patterns of five species-rich groups, mostly herbaceous plants, in 74 forest plots along three climatically contrasting elevational transects from humid tropical lowland vegetation up to cloud forests at Los Tuxtlas, Mexico. We recorded 278 plant species, with ferns being the most species-rich group followed by orchids, bromeliads, aroids, and piperoids. The most striking results were the contrasting patterns and model results for terrestrial and epiphytic taxa. Whereas the richness of all terrestrial species taken together did not change significantly with elevation, vascular epiphytes showed increasing species numbers with altitude. However, a number of individual terrestrial taxa showed also significant elevation-related changes: aroids showed a marked decline with hight, orchids and piperoids increased, and ferns displayed a hump-shaped pattern with highest richness in mid-altitudes. Among the epiphytes, aroids declined while most other groups increased with altitude. This distinction is relevant for projections of responses of plant communities to climate change, which will lead to increased temperatures and to changing precipitation and cloud condensation regimes and thus will likely affect terrestrial and epiphytic species in different ways