Tendências evolutivas em nicotiana alata link & otto (solanaceae): relações entre sucesso reprodutivo e características funcionais em uma população do sul do Brasil

Abstract

The natural selection act in distinctive floral traits and it is important to reproductive success maintence in plant populations. The floral traits variations have a great effect to verify the natural selection effects in short long time. Nicotiana alata shows hawkmoth flowers traits. Hawkmoths are recognized to presents population fluctuation that can affect the reproductive success. This study was made in 2011 and 2012 years in Sao Gabriel municipality, Rio Grande do Sul state and addressed the follow questions: (i) The corolla tube length and corolla lobes variations affect the reproductive success in this population? (ii) Is there variation in the reproductive success along to flowering season? (iii)The floral longevity could be a trait susceptible to natural selection in the population studied? The seed set is not correlate to corolla length variations (r = 0.31; p = 0.07) neither the display floral area (r = 0.35; p = 0.11). However, was observed a significative variations in the corolla length between 2011 (74.75 mm } 12.28) and 2012 (63.94 mm } 6.29) (T Test, t = 6.24; p < 0.0001). The frequence of intermediate categories of corolla length (60 to 75 mm) increases in 2012 and higher fruit and seed set was observed to this category (100%, 1078.9 seeds } 327.29). The same reproductive parameters presents variation along to flowering season with higher values in the beginning with 100% of fruit set and 1110.88 seeds } 378.18 versus 73 % of fruit set and 597.04 seeds } 459,03 in the end of flowering (ANOVA, F= 8.22, p = 0.0002). Pollen limitation was observed only in the intermediated phases of flowering (T Test: phase II, t = 3.60, p = 0.0002, phase III t = 3.09, p = 0.0023). The floral longevity decreasing (9 to 7 days) and there was variation in the fruit set between the different time of flower exposition (ƒÔ2= 15.88; p= 0.001). The population studied presents variation in different floral attributes that promote distinctive evolutionary tendencies to this population. These results indicate that ecological phenomena, like pollen limitation, Allee Effect and intraspecific competition could be occur spatialy and temporaly and traits associated to success reproductive can be more susceptible to variations in short long time.