Reproductive isolation in sympatric Salvia species sharing a sole pollinator

doi:10.17520/biods.2017039

Abstract

Abstract:

Reproductive isolation (RI) is one of the key factors for speciation and diversity maintenance, however, there are differences in formation stage, means, and strength of RI for different species. To assess the effects and the significance of reproductive isolation in Salvia species, we compared flowering, pollination, and reproduction characteristics of Salvia liguliloba and S. bowleyana, which grow sympatrically and have overlapping flowering periods in the Tianmu Mountain, Zhejiang. Furthermore, artificial hybridization between the two species were conducted to estimate and understand their genetic compatibility and reproductive isolation. Results indicated that the two Salvia species considerably differed in their flower morphological structures, inflorescence organization, and the number of flowers produced per inflorescence. Bombus trifasciatus is the sole pollinator for these two species during the overlapping flowering period. However, different visitation behavior and floral structure (P < 0.05) leads to obviously different pollination patterns between the two species. Pollen is deposited on distinctly separate areas of the pollinator’s body in a manner precluding contact with any heterospecific Salvia stigmata. Under natural condition, the two species are equally successful in reproduction (natural seed set > 87%). Artificial pollination and hybridization experiments between these two species showed that they have a higher genetic compatibility. The cross seed sets are 77.8 ± 10.7% and 78.7 ± 11.2% when the two species are reciprocally cross parents. Our research suggests that for the two Salvia species lacking genetic incompatibility systems and relying on pollinators for outcrossing, there are differences in floral structures and pollen placement sites. The mechanical isolation (a form of pre-pollination RI) prevents heterospecific pollen interference and natural hybridization of the two different species that grow sympatrically and have overlapping flowering periods, and also maintains species diversity and the constancy of species heredity.

http://jtp.cnki.net/bilingual/detail/html/SWDY201706005

Key words: mechanical isolation, genetic compatibility, species diversity, natural hybridization, Bombus trifasciatus

Yukun Wei, Yanbo Huang, Guibin Li. Reproductive isolation in sympatric Salvia species sharing a sole pollinator[J]. Biodiv Sci, 2017, 25(6): 608-614.

Figures/Tables 5

References 21

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	花冠长 Corolla length	花冠宽 Corolla width	花冠高 Corolla height	冠筒长 Tube length	冠口高 Entrance height	冠筒口高 Tube entrance height	冠筒口宽 Tube entrance width	花丝长 Filament length	药隔长 Connective length	雌蕊长 Pistil length
舌瓣鼠尾草 S. liguliloba	23.7 ± 0.74^a	5.31 ± 0.34^a	7.30 ± 0.67^b	19.5 ± 0.8^a	4.87 ± 0.61^b	4.87 ± 0.61^a	4.41 ± 0.52^a	2.39 ± 0.14^b	5.19 ± 0.33^b	23.7 ± 0.43^b
南丹参 S. bowleyana	22.8 ± 1.10^b	4.47 ± 0.26^b	16.6 ± 0.94^a	12.4 ± 0.76^b	11.2 ± 0.80^a	4.47 ± 0.28^a	3.21 ± 0.23^b	4.30 ± 0.26^a	14.3 ± 0.68^a	26.1 ± 1.85^a
P	0.0407	0.000	0.000	0.000	0.000	0.0585	0.000	0.000	0.000	0.0011

	花冠长 Corolla length	花冠宽 Corolla width	花冠高 Corolla height	冠筒长 Tube length	冠口高 Entrance height	冠筒口高 Tube entrance height	冠筒口宽 Tube entrance width	花丝长 Filament length	药隔长 Connective length	雌蕊长 Pistil length
舌瓣鼠尾草 S. liguliloba	23.7 ± 0.74^a	5.31 ± 0.34^a	7.30 ± 0.67^b	19.5 ± 0.8^a	4.87 ± 0.61^b	4.87 ± 0.61^a	4.41 ± 0.52^a	2.39 ± 0.14^b	5.19 ± 0.33^b	23.7 ± 0.43^b
南丹参 S. bowleyana	22.8 ± 1.10^b	4.47 ± 0.26^b	16.6 ± 0.94^a	12.4 ± 0.76^b	11.2 ± 0.80^a	4.47 ± 0.28^a	3.21 ± 0.23^b	4.30 ± 0.26^a	14.3 ± 0.68^a	26.1 ± 1.85^a
P	0.0407	0.000	0.000	0.000	0.000	0.0585	0.000	0.000	0.000	0.0011

	单株花序总数 No. of infloresce- nce in individual plant	假圆锥花序分枝数 No. of branch in a false panicle	假总状花序的轮伞花序数 No. of verticillaster in a false raceme	轮伞花序小花总数 No. of flower in a verticillaster	轮伞花序同时开放小花数 No. of flowering in a verticillaster	单株总花数 Total no. of flower in individual plant	单株总开花数 Total no. of flowering in individual plant
舌瓣鼠尾草 S. liguliloba	2.0±2.1^a (n = 35)	2.0±1.9^b (n = 39)	9.3±2.4^a (n = 83)	5.6±1.1^b (n = 93)	1.4±1.7^b (n = 234)	262±299^b (n = 26)	21±30^a (n = 36)
南丹参 S. bowleyana	2.2±0.45^a (n = 5)	5.8±3.0^a (n = 11)	9.5±1.9^a (n = 40)	9.8±1.9^a (n = 160)	1.8±1.0^a (n = 160)	891±472^a (n = 5)	48±56^a (n = 16)
P	0.681	0.0020	0.7166	0.000	0.0053	0.0005	0.089

	单株花序总数 No. of infloresce- nce in individual plant	假圆锥花序分枝数 No. of branch in a false panicle	假总状花序的轮伞花序数 No. of verticillaster in a false raceme	轮伞花序小花总数 No. of flower in a verticillaster	轮伞花序同时开放小花数 No. of flowering in a verticillaster	单株总花数 Total no. of flower in individual plant	单株总开花数 Total no. of flowering in individual plant
舌瓣鼠尾草 S. liguliloba	2.0±2.1^a (n = 35)	2.0±1.9^b (n = 39)	9.3±2.4^a (n = 83)	5.6±1.1^b (n = 93)	1.4±1.7^b (n = 234)	262±299^b (n = 26)	21±30^a (n = 36)
南丹参 S. bowleyana	2.2±0.45^a (n = 5)	5.8±3.0^a (n = 11)	9.5±1.9^a (n = 40)	9.8±1.9^a (n = 160)	1.8±1.0^a (n = 160)	891±472^a (n = 5)	48±56^a (n = 16)
P	0.681	0.0020	0.7166	0.000	0.0053	0.0005	0.089

	相对频次 Relative frequency	单花访问时间 Visit time per flower (s)	活跃度 Activity rate	访花频率 Visitation rate
舌瓣鼠尾草 S. liguliloba	0.14 ± 0.017^b (n = 3)	2.01 ± 0.85 ^a (n = 30)	9.71 ± 3.15^b (n = 7)	1.36 ± 0.17^b (n = 3)
南丹参 S. bowleyana	0.86 ± 0.017^a (n = 3)	1.80 ± 0.63 ^a (n = 30)	16.2 ± 3.4 ^a (n = 52)	13.9 ± 0.28^a (n = 3)
P	0.000	0.2758	0.000	0.000