How to approach the study of syndromes in macroevolution

Syndromes, wherein multiple traits evolve convergently in response to a shared selective driver, form a central concept in ecology and evolution. Recent work has questioned the utility and indeed the existence of some of the classic syndromes, such as pollination and seed dispersal syndromes. Here, we discuss some of the major issues that have plagued research into syndromes in macroevolution. First, observation of co-evolving traits (sometimes called “trait syndromes'') is often used as evidence of adaptation to a particular driver, even when the link between traits and adaptation is not well-tested. Second, the study of syndromes often uses a biased sampling approach, focusing on the most extreme examples, which may obscure significant continuous variation between traits. Finally, researchers often focus on the traits that are easiest to measure even though these may not be the most directly relevant to adaptive hypotheses. We argue that these issues can be avoided by combining macroevolutionary studies of trait variation across entire clades with explicit tests of adaptive hypotheses, and that taking this approach will lead to a better understanding of syndrome-like evolution and its drivers.

FENOLOGIA REPRODUTIVA DE RUBIACEAE JUSS. NA MATA ATLÂNTICA PARAIBANA

Phenological studies help determine the reproductive and vegetative patterns of plants, contributing to knowledge about dynamics in an environment. We studied the reproductive phenological patterns of five Rubiaceae species in an Atlantic Forest area, evaluating their seed dispersal syndromes and the effects of climatic variables on flowering and fruiting phenology. We monitored reproductive individuals of five species biweekly from February 2015 to February 2016 (one-year period). For each reproductive phenophase, we evaluated the Fournier index and intrapopulational synchronicity. Spearman’s rank correlation was used to determine possible correlations between phenological phenophases and rainfall, temperature and photoperiod. Seed dispersal syndromes were based on morphological analysis and Van der Pijl classification. The Rubiaceae community showed a continuous pattern of flowering and fruiting. However, when analysing phenological patterns by species, there was a higher concentration of phenophases and synchronicity of populations in the rainy season. Flowering and fruiting were positively correlated with temperature and historical average rainfall. Zoochory was the predominant seed dispersal syndrome, indicating the importance of the Rubiaceae family as a year-round resource for frugivorous communities. Temperature and rainfall regulate the reproductive phenophases similarly, resulting in a high level of synchrony between them.

PATTERNS OF SEED DISPERSAL SYNDROMES AT DIFFERENT ALTITUDES IN THE SEMIARID REGION

The objective of this study was to assess the patterns of seed dispersal syndromes of woody plants from nine forest fragments distributed at different altitude levels on the Araripe plateau, in Pernambuco, Brazil. For data collection, we divided the altitudes within the region into three categories: lower level (altitudes ≤600 m); intermediate level (600< altitudes <750 m); and higher level (altitudes ≥750 m). We registered nine fragments, three per altitude level. In each of them, we distributed 20 rectangular sampling units with 250 m², totaling a sampling area of 4.5 ha. We quantified, collected, and identified woody plants with a diameter at breast height higher than or equal to 0.1 m (DBH 1.30 m ≥0.10 m). We characterized the dispersal syndrome according to the characteristics of the fruits and seeds and based on a literature review. In the whole region, we sampled 6,987 individuals, distributed in 35 families, 82 genera, and 153 species. Approximately 41% of all individuals are dispersed by animals, 37% by the plant’s own mechanisms, and 21% by the wind. In terms of dispersal, 47% of species were classified as zoochorous, 23% as autochorous, and 14% as anemochorous. Seed dispersal patterns vary according to altitude levels, with higher regions tending to present greater representativeness of biotic dispersers and lower ones, abiotic.

A numerical analysis of Ephedra L. based on reproductive features

A numerical analysis of Ephedra L. was conducted based on 29 characters of reproductive organs. The results indicate that species are not grouped according to their geographic ranges, sect. Alatae is in one group, sect. Asarca excluding E. cutleri and E. viridis consists of a Eu-asarca group while sect. Ephedra plus E. cutleri and E. viridis of the traditional sect. Asarca make up a third expanded Ephedra group. The Old World sect. Monospermae including E. rhytidosperma, E. equisetina, E. nebrodensis, E. monosperma and E. procera was rediscovered in this study while those Himalayan endemic species (e.g. E. minuta, E. likiangensis, E. saxatilis, E. dawuensis and E. gerardiana) used to be grouped in the Old World sect. Monospermae are clustered together with sect. Scandentes including E. foeminea, E. ciliata, E. altissima and E. fragilis. This study further confirms that the adaptive seed dispersal syndromes of sect. Asarca have originated for not only once. Some new features are introduced as related to dispersal, e.g. weight and size of seeds, and nature and thickness of the outer envelope.DOI: http://dx.doi.org/10.3329/bjpt.v20i1.15464Bangladesh J. Plant Taxon. 20(1): 51-60, 2013 (June)

Life-forms, pollination and seed dispersal syndromes in plant communities on ironstone outcrops, SE Brazil

Rock outcrops play an important role in enhancing plant diversity in montane ecosystems. Ironstone outcrops (cangas) are among the lithotypes less known and most threatened in SE Brazil, due to mining activities. Besides species composition, a key feature to promote their conservation and restoration is the knowledge of the community prevalent life-forms, pollination and seed dispersal syndromes. The analyses were done based on published floristic surveys of cangas in SE Brazil. A total of 353 species of angiosperms (70 families) were assigned to one of the two predominant physiognomies (open areas and forest islands) on ironstone outcrops. Sixteen families responded for 70% of all species. Compared to Raunkiaer's spectrum, phanerophytes were over- and therophytes were under-represented. Phanerophytes were the predominant life-form in forest islands, while hemicryptophytes were outstanding in open areas. Entomophily was the dominant pollination syndrome in both habitats. Zoochory was dominant in forest islands and ranked last in open areas, where anemochory and autochory prevailed. Considering that both forest islands and open areas are subjected to the same climatic conditions, the results corroborate the influence of geoedaphic components in the three traits analysed.