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BACKGROUND:The tendency of animals and plants to independently develop similar features under similar evolutionary pressures - convergence - is a widespread phenomenon in nature. In plants, convergence has been suggested to explain the striking similarity in life form between the giant lobelioids (Campanulaceae, the bellflower family) of Africa and the Hawaiian Islands. Under this assumption these plants would have developed the giant habit from herbaceous ancestors independently, in much the same way as has been suggested for the giant senecios of Africa and the silversword alliance of Hawaii.RESULTS:Phylogenetic analyses based on plastid (rbcL, trnL-F) and nuclear (internal transcribed spacer [ITS]) DNA sequences for 101 species in subfamily Lobelioideae demonstrate that the large lobelioids from eastern Africa the Hawaiian Islands, and also South America, French Polynesia and southeast Asia, form a strongly supported monophyletic group. Ancestral state reconstructions of life form and distribution, taking into account phylogenetic uncertainty, indicate their descent from a woody ancestor that was probably confined to Africa. Molecular dating analyses using Penalized Likelihood and Bayesian relaxed clock approaches, and combining multiple calibration points, estimate their first diversification at ~25-33 million years ago (Ma), shortly followed by several long-distance dispersal events that resulted in the current pantropical distribution.CONCLUSION:These results confidently show that lobelioid species, commonly called 'giant', are very closely related and have not developed their giant form from herbaceous ancestors independently. This study, which includes the hitherto largest taxon sampling for subfamily Lobelioideae, highlights the need for a broad phylogenetic framework for testing assumptions about morphological development in general, and convergent evolution in particular.
Have giant lobelias evolved several times independently? Life form shifts and historical biogeography of the cosmopolitan and highly diverse subfamily Lobelioideae (Campanulaceae)
<unk>Mwaka wa Uchapishaji: PIMBO: Mwelekeo wa wanyama na mimea ya kuendeleza kwa kujitegemea sifa sawa chini ya shinikizo sawa la mageuzi - kuungana - ni jambo la kawaida katika asili. Katika mimea, imedokezwa kuwa kuungana kunaweza kueleza kufanana kwa namna ya maisha kati ya lobelioids kubwa (Campanulaceae, familia ya bellflower) ya Afrika na Visiwa vya Hawaii. "Kutokana na utafiti wa ""kijana"" na ""kijana"" katika jamii ya lobelia, mimea ya aina ya lobelia ya Afrika ya Mashariki, Hawaii, Amerika ya Kusini, Polynesia ya Kifaransa na Asia ya Kusini-Mashariki, inaonyesha kwamba lobelia kubwa ya Afrika ya Mashariki, Visiwa vya Hawaii, na pia Amerika ya Kusini, Polynesia ya Kifaransa na Asia ya Kusini-Mashariki, huunda kundi la monophyletic." Utaratibu wa kuunda upya hali ya mababu ya aina ya maisha na usambazaji, kwa kuzingatia kutokuwa na uhakika wa phylogenetic, unaonyesha asili yao kutoka kwa babu wa mbao ambaye labda alikuwa mdogo kwa Afrika. Uchunguzi wa tarehe ya molekuli kwa kutumia Penalized Likelihood na Bayesian Relaxed Clock, na kuunganisha pointi nyingi za calibration, inakadiria utofauti wao wa kwanza katika ~ 25-33 milioni ya miaka iliyopita (Ma), ikifuatiwa na matukio kadhaa ya kutawanyika kwa umbali mrefu ambayo yalisababisha usambazaji wa sasa wa pantropical. Utafiti huu, ambao unajumuisha sampuli kubwa zaidi ya taxon kwa subfamily Lobelioideae, inasisitiza hitaji la mfumo mpana wa phylogenetic kwa majaribio ya dhana kuhusu maendeleo ya morphological kwa ujumla na mageuzi ya convergent kwa maalum. Je, lobelia kubwa zimebadilika-badilika mara kadhaa kwa kujitegemea? Mabadiliko ya aina ya maisha na historia ya kibiogeografia ya cosmopolitan na tofauti sana subfamily Lobelioideae (Campanulaceae)