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Dick Boyd has written a number of papers concerning Natural Kinds. Many can be found on his website here: Richard-Boyd.net
Wilson, Brigandt, and Barker each have additional work describing their take on HPC views in biology.
Wilson, R. A. (1999), Realism, Essence, and Kind: Resuscitating Traditional Species Essentialism?
Wilson, R. A. (2005) Genes and the Agents of Life: The Individual in the Fragile Sciences: Biology, Cambridge University Press.
Brigandt, I. (2009) Natural kinds in evolution and systematics: metaphysical and epistemological considerations. Acta Biotheoretica 57: 77–97.
For a critical view, see
Ereshefsky, M. and Matthen, M. (2005) Taxonomy, Polymorphism and History: An Introduction to Population Structure Theory. Philosophy of Science 72, pp. 1-21.
Ereshefsky, M. (2009) Natural Kinds in Biology Routledge Encyclopedia of Philosophy.