An annotated list of marine Chlorophyta from the Pacific Coast of the Republic of Panama with a comparison to Caribbean Panama species

Recent study of marine macroalgal diversity of the Republic of Panama has led to a substantial increase in the number of seaweed species documented for the country. In this updated list of marine algae based on collections made in 1999 and reports from the literature, 44 Chlorophyta (43 species and one variety) are documented for the Pacific coast of Panama, including 27 new records. A comparison of chlorophyte diversity along Caribbean and Pacific coasts revealed greater diversity at nearly all taxonomic levels in the Caribbean flora. Differences in environmental regime (e.g., absence of sea grasses, lower abundance and diversity of hermatypic corals, and greater tidal range along the Pacific coast) explained some of the discrepancy in diversity across the isthmus. Fifteen taxa were common to Caribbean and Pacific coasts, but the number of amphi-isthmian taxa nearly doubled when taxa from nearby floras were included in the estimate. These taxa may represent daughter populations of a formerly contiguous population that was severed by the emerging Central American Isthmus. As indicated by their distribution throughout all tropical oceans, survivors of this transition are probably species that tolerate a broad range of environmental conditions, but some may represent recent introductions mediated by natural or anthropogenic vectors.