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Rising global temperatures are often identified as the key driver impacting ecosystems and the services they provide by affecting biodiversity structure and function. A disproportionate amount of our understanding of biodiversity and function is from short‐term experimental studies and static values of biodiversity indices, lacking the ability to monitor long‐term trends and capture community dynamics. Here, we analyse a biennial dataset spanning 32 years of macroinvertebrate benthic communities and their functional response to increasing temperatures. We monitored changes in species' thermal affinities to examine warming‐related shifts by selecting their mid‐point global temperature distribution range and linking them to species' traits. We employed a novel weighted metric using Biological Trait Analysis (BTA) to gain better insights into the ecological potential of each species by incorporating species abundance and body size and selecting a subset of traits that represent five ecosystem functions: bioturbation activity, sediment stability, nutrient recycling and higher and lower trophic production. Using biodiversity indices (richness, Simpson's diversity and vulnerability) and functional indices (richness, Rao's Q and redundancy), the community structure showed no significant change over time with a narrow range of variation. However, we show shifts in species composition with warming and increases in the abundance of individuals, which altered ecosystem functioning positively and/or non‐linearly. Yet, when higher taxonomic groupings than species were excluded from the analysis, there was only a weak increase in the measured change in community‐weighted average thermal affinities, suggesting changes in ecosystem functions over time occur independently of temperature increase‐related shifts in community composition. Other environmental factors driving species composition and abundance may be more important in these subtidal macrobenthic communities. This challenges the prevailing emphasis on temperature as the primary driver of ecological response to climate change and emphasises the necessity for a comprehensive understanding of the temporal dynamics of complex systems. [ABSTRACT FROM AUTHOR]

Climate change is challenging species' abilities to respond and function. In the Arctic, shifts in temperature and ice cover are disrupting established biological interactions and thereby ecosystem structure and function. By examining epibenthic communities in coastal and continental shelf habitats of Northeast Greenland that have been ice-locked for centuries, we provide a contemporary baseline of benthic functional diversity through a trait-based approach. We show clear trends in biodiversity and traits from a priori defined groups of fjord, shelf, shelf break, and slope habitats. With biodiversity and functional indices, we identified how fjord and shelf communities could be vulnerable to current and future changes in climate conditions. Using a hierarchical model of species communities (HMSC) we found taxa occurrences, regardless of taxonomic relatedness, were mainly driven by changes in depth, salinity, and oxygen and less so by temperature. Though rising global temperatures are undoubtedly altering the physiochemical structure of the shelf area, our study underscores the significance of often-overlooked environmental factors in Arctic climate change studies. Moreover, we highlight how species traits have a significant role in forming and maintaining community composition by explaining a high amount of among-taxa variation in taxa occurrences and taxa responses to the environment. While the significance of this is not known in relation to community resilience, as Arctic shelf processes intensify (e.g., Atlantification), changes in benthic communities and their ecological roles will ultimately affect ecosystem functioning and the broader dynamics of complex seascapes. • Complex seascapes across continental shelves drive diverging traits of benthos. • Arctic benthos responds to depth, oxygen, and salinity more than temperature. • Benthic community traits are central in explaining taxa occurrences. [ABSTRACT FROM AUTHOR]

Several subspecies are defined within Codium fragile, including the invasive C. fragile ssp. fragile, first reported in New Zealand in 1973. An endemic subspecies, C. fragile ssp. novae-zelandiae, is also found throughout New Zealand. The two subspecies exhibit morphological and molecular variation, although these have never been evaluated together. We compared variation between subspecies at locations in Auckland, identifying subspecies using rps3- rpl16 DNA sequence data, and assessing gross morphological differences, anatomical utricle characters and morphometrics. The taxonomic utility of the morphometric data sets was assessed by linear discriminant analysis. Utricle characters and measurements varied within individual thalli and between different preservation methods. The phenotypes of both subspecies were highly variable and influenced by environment. Accurate subspecies delimitation using morphological data was not possible; the discriminant analyses performed no better than chance for all combinations of the morphological data. Specimens from New Zealand, Canada, Australia and Ireland were sequenced using both the rps3- rpl16 and tufA plastid markers. The tufA elongation factor was shown to be a good candidate for differentiating subspecies of C. fragile. This marker is twice the length of the rps3- rpl16 spacer, shows greater variation between ssp. fragile and novae-zelandiae, and is less prone to sequencing error. A simple restriction enzyme digest of the tufA amplicon can distinguish ssp. fragile and ssp. novae-zelandiae. Our study expands the known range of the ssp. fragile in New Zealand, including the first record of this subspecies from the west coast of Auckland, and points to a need to re-evaluate morphological and molecular criteria for subspecies currently defined within C. fragile. [ABSTRACT FROM AUTHOR]