Exploring the role of genetic diversity and relatedness in tree seedling growth and mortality: A multispecies study in a Bornean rainforest. (12th February 2020)

• Record Type: Journal Article
• Authors: Tito de Morais, Claire; Kettle, Chris J.; Philipson, Christopher D.; Maycock, Colin R.; Burslem, David F. R. P.; Khoo, Eyen; Ghazoul, Jaboury
• Editors: Zuidema, Pieter
• Is Part Of: Journal of ecology. Volume 108:Number 3(2020:May)
• Page Start: 1174
• Page End: 1185
• Publication Date: 2020-02-12
• Subjects: genetic relatedness -- heterozygosity -- population dynamics -- rainforest -- seedling growth and mortality; Plant ecology -- Periodicals; 577.05
• DOI: 10.1111/1365-2745.13331
• Languages: English
• ISSNs: 0022-0477

Abstract

Abstract: Where conspecific seedlings occur at high densities, density‐dependent processes tend to depress their performance and survival relative to co‐occurring heterospecifics. We extend this observation to within‐species genetic diversity and relatedness. We posit that seedling growth and survival increase where there is higher genetic diversity, and lower relatedness, among seedling populations, under the expectation that increased genetic dissimilarity among conspecific seedlings affords greater resistance to pathogens. We used estimates of individual seedling genetic diversity (multilocus heterozygosity (sMLH)) and genetic relatedness among conspecific seedlings (pairwise kinship coefficients (LRI)), under high and low conspecific seedling density, coupled with censuses of seedling growth and mortality over 30 months to explore the role of genetic diversity and relatedness on growth and mortality of 1, 485 seedlings of four dipterocarp species in an undisturbed Bornean tropical rainforest. We hypothesized that more genetically diverse and less related co‐occurring seedlings would display higher survival and growth rates. In three of our four species, lower genetic diversity increased the probability of mortality over 30 months. We observed no effect of genetic diversity on relative growth rates. Contrary to our expectations, only one species showed a negative effect of increased relatedness on mortality. In two of the four species studied, seedlings that were more genetically related to neighbouring conspecific seedlings in the sample plot were less likely to die, but grew more slowly. Synthesis . Our results confirm that genetic diversity and relatedness among seedlings shape survival probabilities differentially across species. In contrast, we found no differences in mortality and growth rates between plots with low and high seedling density. Our results suggest that a greater abundance of pollen donors could contribute to cohort seedling survival in some species, though not all, and the specific mechanisms by which genetic relatedness determines seedling demography remain uncertain. These results have conservation and management implications in view of changing patterns of gene flow in fragmented, exploited and degraded tropical rainforests, which might differentially influence natural regeneration among species. Abstract : Seedling of dipterocarp species Shorea gibbosa following a masting event in Sepilok Forest Reserve, Sabah, Malaysia. Copyright Chris J. Kettle. Abstract : Apabila anak benih berlaku pada kepadatan yang tinggi, proses kebergantungan kepadatan lebih terjejas pertumbuhannya berbanding heterscpecifics. Kami memanjangkan pemerhatian dalam spesies kepelbagaian genetik dan perkaitannya. Kami mendapati bahawa pertumbuhan anak benih dan kemadiriannya meningkat iaitu kepelbagaian genetik, perkaitan yang rendah di kalangan populasi anak benih, dalam jangkaan bahawa ketidaksamaan genetik meningkat di kalangan anak benih conspecifik terhadap peningkatan resisten terhadap patogen. Kami menganggarkan individu kepelbagaian genetik anak benih (sMLH) dan perkaitan genetik di kalangan anak benih conspecific (LRI), di bawah kepadatan anak benih conspesific yang rendah dan tinggi, beberapa pemilihan pertumbuhan dan kematian anak benih melebih 30 bulan untuk melihat peranan kepelbagaian genetik dan perkaitannya terhadap pertumbuhan dan kematian 1485 anak pokok dari empat spesies dipterokarp di kawasan hutan hujan tropika yang belum terganggu. Hipotesis kami adalah bahawa lebih banyak kepelbagaian genetik dan kurang perkaitan ko perlakuan anak pokok maka lebih tinggi kadar pertumbuhannya. Tiga dari empat spesies kepelbagaian genetik yang rendah meningkatkan kebarangkalian kematian lebih 30 bulan. Kami telah memerhatikan bahawa tiada kesan kepelbagaian genetik terhadap kadar pertumbuhan relatif. Bertentangan dengan jangkaan kami, hanya satu spesies yang menunjukkan kesan negatif terhadap peningkatan perkaitan kematian. Dua daripada empat spesies yang dikaji, anak pokok yang lebih secara genetik kepada anak pokok conspecifik berhampiran dalam sampel plot adalah kurang untuk mengalami kematian, tetapi pertumbuhan agak perlahan. Sisntesis: Keputusan kami mengesahkan bahawa kepelbagaian genetik dan perkaitan di kalangan anak benih membentuk kebarangkalian kemadirian yang berbeza untuk semua spesies. Sebaliknya, kami mendapati tiada perbezaan dalam kadar kematian dan kadar pertumbuhan di antara plot pada kedua‐dua kepadatan anak benih tinggi dan rendah. Keputusan kami mencadangkan bahawa taburan debunga yang lebih besar boleh menyumbangkan kepada kemandirian anak benih dalam kebanyakan spesies walaupun bukan semua, dan mekanisma spesifik iaitu perkaitan genetik menentukan demografi anak benih masih tidak jelas. Keputusan ini memberikan implikasi pemeliharaan dan pengurusan dalam perubahan corak kitaran gen yang tidak utuh, yang digunkan, rosak dalam hutan hujan tropika yang mungkin mempengaruhi regnerasi asli secara berbeza dalam kalangan spesies.