Sains Malaysiana 44(1)(2015): 75–81

Quantifying the Relative Importance of Climate and Habitat on Structuring the Species and Taxonomic Diversity of Aquatic Plants in a Biodiversity Hotspot of Tropical Asia

(Mengukur Kepentingan Relatif Iklim dan Habitat Terakhir Penstrukturan Spesies dan Kepelbagaian

Taksonomi Tumbuhan Akuatik di Bintik Panas Kepelbagaian Biologi Asia Tropika)

YOUHUA CHEN*

Department of Renewable Resources, University of Alberta, Edmonton, T6G 2H1

Canada

Received: 13 February 2014/Accepted: 3 July 2014

ABSTRACT

It has not been well known how climate and habitat variables will influence the distribution of plant species to some extents at mesoscales. In this report, by using the distribution of aquatic plants in Western Ghats, a biodiversity hotspot in tropical Asian region, I quantify the relative importance of climate and habitat variables on structuring spatially species richness and taxonomic diversity patterns using structural equation modeling. All the sampling qudrats in the region used for the study has a spatial resolution of 0.5 latitude × 0.5 longitude. The results showed that species richness is high in both northern and southern part of the region, while low in the middle part. In contrast, taxonomic distinctiveness is relatively homogeneous over all the sampling quadrats in the region. Structural equation modeling suggested that taxonomic distinctiveness patterns of aquatic plants in the region follow temperature (partial regression coefficient=0.31, p<0.05) and elevational (partial regression coefficient=0.31, p<0.05) gradients, while richness patterns cannot be explained by any of the currently used variables. In conclusion, environmental variables that are related to taxonomic distinctiveness would not be related to richness, given the fact that these two quantities are orthogonal more or less. Both climate and habitat are equally influential on taxonomic distinctiveness patterns for aquatic plants in Western Ghats of India.

Keywords: Climatic envelope; environmental correlation; Linnaeus classification; WorldClim database

ABSTRAK

Masih belum diketahui bagaimanakah pemboleh ubah iklim dan habitat akan mempengaruhi taburan spesies tumbuhan mengikut skalameso. Dalam laporan ini, dengan menggunakan taburan tumbuhan akuatik di Barat Ghats yang merupakan titik panas kepelbagaian biologi di rantau Asia tropika, saya menentukan kepentingan pemboleh ubah iklim dan habitat terakhir penstrukturan reruang kekayaan spesies dan taksonomi kepelbagaian corak menggunakan pemodelan persamaan struktur. Semua sampel quadrat yang digunakan untuk kajian di rantau ini mempunyai resolusi reruang 0.5 latitud × longitud 0.5. Hasil kajian menunjukkan bahawa kekayaan spesies adalah tinggi di bahagian utara dan selatan rantau ini, manakala rendah di bahagian tengah. Sebaliknya, perbezaan taksonomi adalah agak seragam ke atas semua sampel quadrat di rantau ini. Pemodelan persamaan struktur mencadangkan bahawa pola perbezaan taksonomi tumbuhan akuatik di rantau ini mengikut suhu (pekali regresi separa = 0.31, p<0.05) dan ketinggian (pekali regresi separa = 0.31, p<0.05) kecerunan, manakala pola kekayaan tidak dapat dijelaskan oleh mana-mana pemboleh ubah yang sedang digunakan. Kesimpulannya, pemboleh ubah alam sekitar yang berkaitan dengan perbezaan taksonomi tidak berkaitan dengan kekayaan, memandangkan kuantiti kedua-duanya adalah lebih atau kurang ortogon. Kedua-dua iklim dan habitat mempengaruhi pola perbezaan taksonomi untuk tumbuhan akuatik di Barat Ghats India.

Kata kunci: Iklim sampul; korelasi alam sekitar; pangkalan data WorldClim; pengelasan Linnaeus

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*Corresponding author; email: youhua@ualberta.ca