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Sea Slugs—“Rare in Space and Time”—But Not Always

National Marine Science Centre, Southern Cross University, Bay Drive, Coffs Harbour, NSW 2450, Australia
Marine Ecology Research Centre, Southern Cross University, Lismore, NSW 2458, Australia
Author to whom correspondence should be addressed.
Diversity 2020, 12(11), 423;
Received: 24 September 2020 / Revised: 26 October 2020 / Accepted: 9 November 2020 / Published: 11 November 2020
(This article belongs to the Section Marine Diversity)
The term “rare in space and time” is often used to typify the spatial and temporal patterns of occurrence of heterobranch sea slugs. However, “rare” in this context has not been clearly defined. In an attempt to provide more insight into the concept of rarity in sea slug assemblages, we analysed abundance data from 209 individual surveys conducted over a 5-year period in a subtropical estuary and a 7-year period on a shallow coastal reef, on the Sunshine Coast, Qld, Australia. Using an ‘intuitive’ method (<10 individuals recorded over the study), and the ‘quartile’ method we assessed numerical rarity (number of individuals of a species seen over the study period) and temporal rarity (frequency of observation). We also assessed numerical rarity using octaves based on log2 abundance bins. The quartile method did not effectively capture either measure of rarity. The octave method, however, fitted closely to subjective classifications of abundance and defined a similar number of species as rare when compared to the intuitive method. Using the octave method, 66% of species in both the estuary and on the reef, were considered as rare. Consequently, we recommend the octave method to allocate abundance classifications. To address the poor fit for temporal classifications based on quartiles, we propose the following as a working model for wider testing: rare ≤25% of surveys; uncommon 26−50%, common 51−75%; and abundant >75%. View Full-Text
Keywords: sea slugs; rarity; abundance; ephemeral; estuary; coastal reef sea slugs; rarity; abundance; ephemeral; estuary; coastal reef
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MDPI and ACS Style

Schubert, J.; Smith, S.D.A. Sea Slugs—“Rare in Space and Time”—But Not Always. Diversity 2020, 12, 423.

AMA Style

Schubert J, Smith SDA. Sea Slugs—“Rare in Space and Time”—But Not Always. Diversity. 2020; 12(11):423.

Chicago/Turabian Style

Schubert, Julie, and Stephen D.A. Smith 2020. "Sea Slugs—“Rare in Space and Time”—But Not Always" Diversity 12, no. 11: 423.

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