Biodiversity may wax or wane depending on metrics or taxa. Yoccoz, N. G., Ellingsen, K. E., & Tveraa, T. Proceedings of the National Academy of Sciences, February, 2018.
Biodiversity may wax or wane depending on metrics or taxa [link]Paper  doi  abstract   bibtex   
Biodiversity changes have proven surprisingly complex to estimate and understand. While there are negative trends at a global scale such as the substantial losses of vertebrate species (1), changes at local scales may show large variation, with no clear overall trend (2, 3). Because assessing and improving the status of biodiversity are at the core of international agreements such as the Convention on Biological Diversity and the associated Aichi Biodiversity Targets for 2020 (4), we need to know when trends in biodiversity may differ and the causes of such differences. In PNAS, Magurran et al. (5) report that different components of biodiversity do not have the same trends over time in tropical freshwater ecosystems, and that these trends differ among taxonomic groups (fishes, invertebrates, and diatoms). Magurran et al. (5) quantify biodiversity changes at 16 river sites in Trinidad over 19 time points covering the dry and wet seasons of 5 y. They collected over 670,000 individuals, which were identified at different resolutions in fishes (species), invertebrates (family), and diatoms (morphospecies) because taxonomy is still poorly known for many groups in the tropics. They focus on two aspects of biodiversity changes: temporal α diversity, measured using the number of species and functions of their relative abundance, and temporal β diversity, which represents change in assemblage composition over time and is measured as turnover in species identities and relative abundance (Fig. 1). Different diversity measures emphasize different characteristics of assemblages (6). Magurran et al. (5) use 11 metrics, ranging from the number of observed or estimated species at a site and metrics emphasizing evenness or dominance to a range of (dis)similarity measures to evaluate compositional differences between assemblages. These are based on either presence/absence or abundance data and emphasize turnover in species identities (species replacement) and nestedness [associated with richness … [↵][1]1To whom correspondence should be addressed. Email: nigel.yoccoz\at\uit.no. [1]: #xref-corresp-1-1
@article{yoccoz_biodiversity_2018,
	title = {Biodiversity may wax or wane depending on metrics or taxa},
	copyright = {© 2018 . Published under the PNAS license.},
	issn = {0027-8424, 1091-6490},
	url = {http://www.pnas.org/content/early/2018/02/09/1722626115},
	doi = {10.1073/pnas.1722626115},
	abstract = {Biodiversity changes have proven surprisingly complex to estimate and understand. While there are negative trends at a global scale such as the substantial losses of vertebrate species (1), changes at local scales may show large variation, with no clear overall trend (2, 3). Because assessing and improving the status of biodiversity are at the core of international agreements such as the Convention on Biological Diversity and the associated Aichi Biodiversity Targets for 2020 (4), we need to know when trends in biodiversity may differ and the causes of such differences. In PNAS, Magurran et al. (5) report that different components of biodiversity do not have the same trends over time in tropical freshwater ecosystems, and that these trends differ among taxonomic groups (fishes, invertebrates, and diatoms).

Magurran et al. (5) quantify biodiversity changes at 16 river sites in Trinidad over 19 time points covering the dry and wet seasons of 5 y. They collected over 670,000 individuals, which were identified at different resolutions in fishes (species), invertebrates (family), and diatoms (morphospecies) because taxonomy is still poorly known for many groups in the tropics. They focus on two aspects of biodiversity changes: temporal α diversity, measured using the number of species and functions of their relative abundance, and temporal β diversity, which represents change in assemblage composition over time and is measured as turnover in species identities and relative abundance (Fig. 1). Different diversity measures emphasize different characteristics of assemblages (6). Magurran et al. (5) use 11 metrics, ranging from the number of observed or estimated species at a site and metrics emphasizing evenness or dominance to a range of (dis)similarity measures to evaluate compositional differences between assemblages. These are based on either presence/absence or abundance data and emphasize turnover in species identities (species replacement) and nestedness [associated with richness … 

[↵][1]1To whom correspondence should be addressed. Email: nigel.yoccoz\{at\}uit.no.

 [1]: \#xref-corresp-1-1},
	language = {en},
	urldate = {2018-02-24},
	journal = {Proceedings of the National Academy of Sciences},
	author = {Yoccoz, Nigel G. and Ellingsen, Kari E. and Tveraa, Torkild},
	month = feb,
	year = {2018},
	pmid = {29440437},
	keywords = {biodiversity, boundaries, collapse},
	pages = {201722626},
	file = {Yoccoz et al. - 2018 - Biodiversity may wax or wane depending on metrics .pdf:C\:\\Users\\rsrs\\Documents\\Zotero Database\\storage\\59E57QFN\\Yoccoz et al. - 2018 - Biodiversity may wax or wane depending on metrics .pdf:application/pdf}
}
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