Functional biogeography of coastal marine invertebrates along the south-eastern Pacific coast

Characterizing the spatial structure of taxonomic and functional diversity
(FD) of marine organisms across regional and latitudinal scales is
essential for improving our understanding of the processes driving species
richness and those that may constrain or enhance the set of species traits
that define the functional structure of communities. Here, we present the
functional diversity of coastal invertebrate macrofaunal species along the
south-eastern Pacific, from 7°N to 56°S, we describe spatial
variation of species traits, and examine the relationship with
environmental variables. We define the functional traits and the
distribution range of 2350 marine macroinvertebrates to calculate eight
metrics of FD. Random forest regression was applied to identify
significant relationships between FD and six environmental variables.
Finally, functional ß-turnover was estimated to detect alongshore shifts
in functional structure and their coincidence with biogeographical
domains. In contrast with taxonomic richness, measures of trait
differences, functional space and functional specialisation increase with
latitude, while functional evenness exhibits a humpback shape, peaking at
mid-latitudes. Functional redundancy decreases significantly poleward,
while indications of vulnerability increase. In contrast to taxonomic
richness, FD was tightly connected to variables indicative of stress and
productivity, such as dissolved oxygen and nutrients. Sea surface
temperature and coastal area best explained the increased FD redundancy
towards the tropics. The high spatial correlation between taxonomic and
functional ß-turnover suggests environmental filters play an important
role in the functional structure of the seascape. Our findings
suggest that processes favouring taxonomic richness are latitudinally
divergent from those favouring functional diversity. Correlations with
environmental variables suggest that increased sea surface temperature and
measures of stability increase redundancy, while variation in dissolved
oxygen and nutrients positively affect functional diversification.
Moreover, the functional diversity patterns suggest low resilience of
high-latitude coastal ecosystems, which are heavily exploited and
threatened by climate change, hence highlighting the urgent need for
effective conservation policies.