[Taxacom] Meliaceae vicariance

[John Grehan]

Speculations such as that proposed by Ken have no merit without some sort
of evidence based inference. The absence in southwestern Australia is part
of a pattern of absence globally and the vicariance explanation accounts
for both together. If there is evidence for other possibilities then they
certainly be considered. At present there appear to be none.

John Grehan

On Fri, Nov 15, 2019 at 12:00 PM Kenneth Kinman via Taxacom <
taxacom at mailman.nhm.ku.edu> wrote:

> Dear All,
>       Much is being made here of the fact that Meliaceae are absent from
> SW Australia, Hawaii, etc. (except for recent introductions) in areas where
> Rutaceae are diverse.   I doubt that it has anything to do with vicariance.
>          Instead it could simply be a case of competitive exclusion of
> Meliaceae by their relatives in Rutaceae.   Especially if Rutaceae spread
> to those areas first.   So this just seems like another case of
> panbiogeographers attacking dispersal wherever they can imagine a
> vicariance alternative.
>                                ---------------Ken
>
> ________________________________
> From: Taxacom <taxacom-bounces at mailman.nhm.ku.edu> on behalf of John
> Grehan via Taxacom <taxacom at mailman.nhm.ku.edu>
> Sent: Wednesday, November 13, 2019 10:36 PM
> To: taxacom <taxacom at mailman.nhm.ku.edu>
> Subject: [Taxacom] Meliaceae vicariance
>
> Hopefully the heading will alert Taxacomers to read this only if interested
> in evidence of vicariance. The monograph on Meliaceae biogeography by Heads
> presents some observations on how this nearly pantropical group along with
> the Simaroubaceae shows evidence of vicariance with respect .to the
> Rutaceae:
>
> “Meliaceae have maximum species numbers in tropical Asia and Malesia (303
> species), with fewer in the Neotropics (189 species), Madagascar (107
> species), and tropical Africa (102 species). However, despite their
> abundance in Malesia and parts of the south-west Pacific, such as Fiji,
> Meliaceae are absent from a vast area of the central Pacific (Fig. 2). This
> area of absence includes Hawaii (where there are five naturalised species),
> the Galapagos (with one naturalised, invasive species), Juan Fernandez
> Islands,
> the Marquesas Islands (one naturalised species), the Society Islands and
> the Cook Islands. This absence exists despite the fact that the family
> includes mangroves (X*ylocarpus *J.Koenig, which ranges east to Tonga) and
> many weedy species.”
>
> “Meliaceae (48 genera, 700 species) form a well-supported clade with the
> smaller, pantropical family Simaroubaceae (22 genera, 100 species) (Koenen
> et al., 2015; Muellner-Riehl et al., 2016). This pair is closest to
> Rutaceae (153 genera, 1975 species). Simaroubaceae are ‘pantropical’, as
> they are present in Africa, Asia and America. However, as with Meliaceae,
> they are absent from Hawaii, the Galapagos, Juan Fernandez Islands, and SE
> Polynesia. In contrast, native Rutaceae are present in all four of these
> areas, and are notably diverse in Hawaii (58 species) and the Marquesas (7
> species) (the Marquesas have only 4% of the land area of Hawaii). The
> absence
> of Meliaceae from many very small islands in the central Pacific, such as
> Rapa or Rarotonga, might be the result of regional extinction with
> continuing subsidence (as the plate moves away from the central Pacific
> spreading ridge and cools). However, the absence from Hawaii and the
> Marquesas seems more significant, as the closely related Rutaceae are so
> diverse there.”The central Pacific allopatry between the two clades,
> Meliaceae + Simaroubaceae, vs Rutaceae, especially on the Hawaii–Marquesas
> sector, can be explained as a trace of the original allopatry caused by
> vicariance between the two clades. If this is correct, similar patterns
> should occur in other groups.
>
> The Hawaiian biota is well known for the high diversity of groups such
> as honeycreepers,
> drosophilids and lobeliads. However, there are also many conspicuous
> absences
> (Heads, 2012). In the Hawaiian flora, many tropical plants, including
> mangroves,
> are absent, despite having very efficient means of dispersal. Other plants
> that characterise tropical shorelines and small islands, either globally
> (such as *Calophyllum *L., *Terminalia *L., *Hernandia *L., *Salicornia
> *L.,
> and *Atriplex *L.) or through the Old World and Pacific (such as
> *Barringtonia
> *J.R.Forst. & G.Forst.), are also absent from the Hawaiian indigenous
> flora. Nevertheless, species of most of these genera thrive in Hawaii as
> introduced weeds.
>
> Transport to Hawaii in mud on birds’ feet is often proposed to explain
> groups’ presence on the islands. Yet some of the most characteristic marsh
> plants, such as Eriocaulaceae and *Juncus *L., are absent from the
> indigenous flora (although several introduced *Juncus *species are now
> widespread). In the same way, many diverse, pantropical groups that are
> abundant in rain forest elsewhere are absent from the indigenous flora of
> Hawaii. These include Cyatheaceae, Araceae sensu stricto, Zingiberales
> (Zingiberaceae, Marantaceae etc.), Melastomataceae, *Ficus *L. (figs),
> and *Piper
> *L. (members of all these groups are naturalised). Thus, although the
> absence of Meliaceae, including the mangrove *Xylocarpus*, from Hawaii
> seems strange, it conforms to a standard pattern that requires a general
> explanation, and regional vicariance is suggested here. Meliaceae are also
> absent from southwestern Australia (as native plants), again, in a region
> where Rutaceae have high diversity."
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