Author Abstract: This panbiogeography special issue of the New Zealand Journal of Zoology represents a significant milestone in the development of biogeography. It has already earned plaudits in this journal, and it illustrates a nodal fusion of the biogeographic philosophy of Leon Croizat with a critical mass of mainly young biologists seeking to go beyond the traditional in addressing the biogeography of one of the more intriguing land masses in the world, New Zealand. The 'Croizatian' tradition of iconoclasm is alive and well.
Note to Readers: Follow links above for author email, full article text, or the publishing scientific journal. Author notes in my review are in quotes.
Review: For our final paper on panbiogeography this week, we'll look at how panbiogeography has developed in New Zealand, a country with some of the strongest proponents of the panbiogeography school of biogeography. This paper is a review (guest editorial) of multiple papers from a conference on panbiogeography that aims to describe the then current state of panbiogeography in New Zealand.
Besides describing how different researchers used panbiogeographic principles, the author gives the following excellent summary (and unique perspective compared to the other panbiogeography papers discussed) of how panbiogeography sits within the field of biogeography as a whole:
"Connor's description of panbiogeography as R-mode biogeography (relationships of taxonomic pattern) is the one I would accept as offering a clear distinction from cladistic (or vicariance) biogeography (Q-mode, relationships of areas), but what is the requisite methodology? It will involve the objective recognition of statistically-significant [my emphasis] generalized tracks in the distribution of taxa, incorporating information on areas of endemism involved, the massing centres of higher taxa (foci of species richness) and the cladistic structure within them in relation to the areas of endemism. Major problems to be addressed [in future work on panbiogeography] include: (1) initial selection of areas of endemism; (2) accumulation of a sample of cladograms sufficiently large to provide statistically-significant results; (3) handling of the cladogram sample in a manner that will optimize recognition and test the significance of recurrent pattern; (4) development of a philosophy for assessing patterns so recognized in terms of process hypotheses. …. Solution of the third problem may also involve an element of phonetics: to devise a measure that will compare clades in a pairwise manner not just on aspects of range or richness, but incorporating information on the representation of areas over the structure of the clade, and then apply a clustering method to recognize groups."
The author notes that addressing such problems (still not fully resolved almost two decades later from the publication of this paper) will allow a "more probabilistic methodology for track analysis, and in the related methods of spanning tree analysis and construction and comparison of biogeographic graphs, both of which attempt to incorporate cladistic structure into track analysis."
This paper also gives a much better (or more refined) definition of "baseline" (introduced earlier this week) as "features of tracks such as the crossing of an ocean or sea basin, or a major tectonic structure, that is interpreted as a diagnostic character uniting individual tracks that may otherwise have little in common." This paper mentions that instead of the "significant subjective element" that some panbiogeographers use in constructing baselines and tracks, that panbiogeographers should rather apply "stricter protocols for track construction and baseline identification… particularly with regard to utilization of Great Circle minimal distances rather than straight lines on Mercator-type projections." In other words, rather than using rectangular maps, researchers should recognize that the Earth is (essentially) spherical and that distances along tracks (important in constructing a minimum spanning tree as one needs to determine minimal distances traversed) should take that point into account.
The author also suggests using archipelagos or groups of islands "such as the Indo-Australian tropics or the Caribbean [as] an opportunity to assess geological hypotheses of [their] evolution in relation to any statistically-significant clusters of patterns." In taking such an approach, the author suggests incorporating the principles of island biogeography (laid out by MacArthur and Wilson in 1967) into panbiogeography theory.
The paper concludes with the words that perhaps biogeographers should take "a more complex view emphasising interacting mutually contingent networks of causes. In practice achieving such a synthesis will require a breakdown of the conceptual and methodological boundaries between biogeography, evolutionary biology, systematics, ecology and geology. Achieving such a dissolution could be seen as the aim of the panbiogeographic synthesis."
Next we'll look at some specific examples of taxonomic gradients and track analyses with the following three papers. As usual, I encourage reading ahead
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