A revision of the check-list of the red (Rhodophyta), green (Chlorophyta) and brown (Ochrophyta, Phaeophyceae) seaweeds of Britain has been compiled and revealed 644 taxa, mostly at species level but including infraspecific taxa: 348 reds, 110 greens and 186 browns. There were 30 additions to the list, notably five newly described species and five new non-native additions. In addition to the check-list, an updated list of non-native species was compiled based on a stringent review of the available evidence. We have listed 31 non-native species (~5% of the flora), although the numbers may be considerably higher and probably include species that are effectively naturalized and perceived to be part of the indigenous flora. The check-list is discussed in relation to the impact of molecular techniques on the identification, taxonomy and phylogeny of species, and points to the need for a comprehensive, in-depth study on the identity and relationships of the seaweeds of Britain.
Aim
Understanding patterns in the abundance of species across thermal ranges can give useful insights into the potential impacts of climate change. The abundant‐centre hypothesis suggests that species will reach peak abundance at the centre of their thermal range where conditions are optimal, but evidence in support of this hypothesis is mixed and limited in geographical and taxonomic scope. We tested the applicability of the abundant‐centre hypothesis across a range of intertidal organisms using a large, citizen science‐generated data set.
Location
UK.
Methods
Species' abundance records were matched with their location within their thermal range. Patterns in abundance distribution for individual species, and across aggregated species abundances, were analysed using Kruskal–Wallis tests and quantile general additive models.
Results
Individually, invertebrate species showed increasing abundances in the cooler half of the thermal range and decreasing abundances in the warmer half of the thermal range. The overall shape for aggregated invertebrate species abundances reflected a broad peak, with a cool‐skewed maximum abundance. Algal species showed little evidence for an abundant‐centre distribution individually, but overall the aggregated species abundances suggested a hump‐backed abundance distribution.
Main Conclusions
Our study follows others in showing mixed support for the abundant‐centre hypothesis at an individual species level, but demonstrates an increased predictability in species responses when an aggregated overall response is considered.
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