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Developmental variation and the evolution of distyly in Hedyotis caerulea (Rubiaceae).

Sampson DA, Krebs RA - Springerplus (2013)

Bottom Line: Pin stigmas first grew at a faster rate than those of thrums, and late in bud development, growth of thrum styles slowed.These rate changes varied among populations, and they differed from the congeneric H. salzmanii.Similar differences between morphs are known in other heterostylous species, and such variation in growth pattern among related species has been used to infer independent evolution of distylous systems.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological, Geological, and Environmental Sciences, Cleveland State University, 2121 Euclid Ave, Cleveland, OH 44115-2406 USA.

ABSTRACT
The development of distyly is thought to arise from differential growth patterns in the pin and thrum morphs. However, few detailed studies exist on the early floral development of distylous flowers, and fewer still look at variation in these traits among populations. Buds at multiple stages of development were collected from five populations of Hedyotis caerulea to quantify how pins and thrums diverge with respect to the initiation, rate, and termination of growth between the stamens and stigmas. The growth rate of anthers varied little spatially across five populations and temporally in both pins and thrums, although thrum anthers grew faster than pin anthers. Dimorphy in stigma height was more complex. Pin stigmas first grew at a faster rate than those of thrums, and late in bud development, growth of thrum styles slowed. These rate changes varied among populations, and they differed from the congeneric H. salzmanii. Similar differences between morphs are known in other heterostylous species, and such variation in growth pattern among related species has been used to infer independent evolution of distylous systems.

No MeSH data available.


Related in: MedlinePlus

Anther development in pin and thrum floral morphs ofH. caerulea. Data of bud lengths (mm) versus height of anthers (mm) were plotted for each bud collected across five populations (A-E), and F provides results for all populations combined, and lines of best fit are simple linear regression of bud length predicting anther height.
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Fig1: Anther development in pin and thrum floral morphs ofH. caerulea. Data of bud lengths (mm) versus height of anthers (mm) were plotted for each bud collected across five populations (A-E), and F provides results for all populations combined, and lines of best fit are simple linear regression of bud length predicting anther height.

Mentions: Variation in growth rate between pins and thrums occurred very early in development (Figures 1 and 2). Across the five populations sampled, the linear term explained most of the variation in the relationship between bud length and anther height in both thrum and pin flowers (Figure 1, linear regressions on raw data are provided in the figure). Results were similar where data were log transformed, and for all five populations combined, a step that provided the power necessary to test for a fit of a second-order term on anther height, no improvement in the model was observed for either morph (Table 1). Thus, the growth of anther height relative to bud length was described by a best fit linear equation where the slope differed significantly between morphs (F1,411 = 21.6, P < 0.001), but minimally among populations. Slopes of both morphs also were significantly (P < 0.001) less than one. In both morphs, the filament served only to attach the anther to the inner surface of the corolla tube and made no contribution to the height of the anther.Figure 1


Developmental variation and the evolution of distyly in Hedyotis caerulea (Rubiaceae).

Sampson DA, Krebs RA - Springerplus (2013)

Anther development in pin and thrum floral morphs ofH. caerulea. Data of bud lengths (mm) versus height of anthers (mm) were plotted for each bud collected across five populations (A-E), and F provides results for all populations combined, and lines of best fit are simple linear regression of bud length predicting anther height.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3755807&req=5

Fig1: Anther development in pin and thrum floral morphs ofH. caerulea. Data of bud lengths (mm) versus height of anthers (mm) were plotted for each bud collected across five populations (A-E), and F provides results for all populations combined, and lines of best fit are simple linear regression of bud length predicting anther height.
Mentions: Variation in growth rate between pins and thrums occurred very early in development (Figures 1 and 2). Across the five populations sampled, the linear term explained most of the variation in the relationship between bud length and anther height in both thrum and pin flowers (Figure 1, linear regressions on raw data are provided in the figure). Results were similar where data were log transformed, and for all five populations combined, a step that provided the power necessary to test for a fit of a second-order term on anther height, no improvement in the model was observed for either morph (Table 1). Thus, the growth of anther height relative to bud length was described by a best fit linear equation where the slope differed significantly between morphs (F1,411 = 21.6, P < 0.001), but minimally among populations. Slopes of both morphs also were significantly (P < 0.001) less than one. In both morphs, the filament served only to attach the anther to the inner surface of the corolla tube and made no contribution to the height of the anther.Figure 1

Bottom Line: Pin stigmas first grew at a faster rate than those of thrums, and late in bud development, growth of thrum styles slowed.These rate changes varied among populations, and they differed from the congeneric H. salzmanii.Similar differences between morphs are known in other heterostylous species, and such variation in growth pattern among related species has been used to infer independent evolution of distylous systems.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological, Geological, and Environmental Sciences, Cleveland State University, 2121 Euclid Ave, Cleveland, OH 44115-2406 USA.

ABSTRACT
The development of distyly is thought to arise from differential growth patterns in the pin and thrum morphs. However, few detailed studies exist on the early floral development of distylous flowers, and fewer still look at variation in these traits among populations. Buds at multiple stages of development were collected from five populations of Hedyotis caerulea to quantify how pins and thrums diverge with respect to the initiation, rate, and termination of growth between the stamens and stigmas. The growth rate of anthers varied little spatially across five populations and temporally in both pins and thrums, although thrum anthers grew faster than pin anthers. Dimorphy in stigma height was more complex. Pin stigmas first grew at a faster rate than those of thrums, and late in bud development, growth of thrum styles slowed. These rate changes varied among populations, and they differed from the congeneric H. salzmanii. Similar differences between morphs are known in other heterostylous species, and such variation in growth pattern among related species has been used to infer independent evolution of distylous systems.

No MeSH data available.


Related in: MedlinePlus