Morphological and molecular evidence demonstrates the amphi-Atlantic distribution of Laurencia catarinensis (Ceramiales, Rhodophyta)

We performed morphological and molecular studies of Laurencia catarinensis from the Canary Islands. This species has an entangled habit, cushion-like tuft formation, cortical cell walls, slightly to markedly projecting near the apex, and lacking lenticular thickenings in medullary cells. We inferred its phylogenetic position by analyzing the chloroplast-encoded rbcL gene sequences from 41 samples. The results demonstrate that specimens of L. catarinensis from the Canary Islands, where it is referred to as L. intricata, and those from Brazil (including specimens from the type locality in Santa Catarina) form a monophyletic clade with low genetic divergence (0-0.9%). In contrast, specimens of L. intricata from the type locality in Cuba, Mexico, and the USA were clearly distinct from L. catarinensis collected in Brazil and the Canary Islands, as shown by high genetic divergence values (4.9-5.7%). The type material of L. catarinensis from Brazil allowed us to identify all samples from the Canarian Archipelago as L. catarinensis. These findings expand the known geographical distribution of L. catarinensis to the eastern Atlantic Ocean and demonstrate an amphi-Atlantic distribution of the species.

Testing the Performance of Fourteen Native Tropical Tree Species in Two Abandoned Pastures of the Lacandon Rainforest Region of Chiapas, Mexico

The rainforest of Mexico has been degraded and severely fragmented, and urgently require restoration. However, the practice of restoration has been limited by the lack of species-specific data on survival and growth responses to local environmental variation. This study explores the differential performance of 14 wet tropical early-, mid- or late-successional tree species that were grown in two abandoned pastures with contrasting land-use histories. After 18 months, seedling survival and growth of at least 7 of the 14 tree species studied were significantly higher in the site with a much longer history of land use (site 2). Saplings of the three early-successional species showed exceptional growth rates. However, differences in performance were noted in relation to the differential soil properties between the experimental sites. Mid-successional species generally showed slow growth rates but high seedling survival, whereas late-successional species exhibited poor seedling survival at both the study sites. Stepwise linear regressions revealed that the species integrated response index combining survivorship and growth measurements, was influenced mostly by differences in soil pH between the two abandoned pastures. Our results suggest that local environmental variation among abandoned pastures of contrasting land-use histories influences sapling survival and growth. Furthermore, the similarity of responses among species with the same successional status allowed us to make some preliminary site and species-specific silvicultural recommendations. Future field experiments should extend the number of species and the range of environmental conditions to identify site generalists or more narrowly adapted species, that we would call sensitive.