My objective is to determine if the abundance of nectarivores at a flower-visitation network are related by biotic factors such as the abundance of flowers, nectar volume or nectar concentration or abiotic factors such as temperature or precipitation.
I have measurements of nectar but they are highly variable. I am not sure what metric should I take if, i.e. I have an average volume of nectar of a set of flowers of a plant of 10 microliters (measured in the morning, covered all night – 12 hours) and then these flowers have a volume of 35 microliters measured after 6 hours of being covered. Should I relate the values in 24 hours? By hour? But the results are going to be very different if you take i.e. 10 or 35 as a base…
How should I address this nectar variability in an analysis to relate its amount with its consumers?
Hi Oscar - Assuming that we are talking about different species here, as a starting point you should compare like with like, so make your comparisons between plant species that have been covered for the same time period, i.e. don't compare a plant species that has been covered for 6 hours with one that's been covered for 12 hours.
Then compare the results you get using one approach with the results obtained using the second approach. You may well find that you find the same pattern (e.g. species with higher nectar accumulation rate over 6 hours attract flower visitors in the same proportion as when you assessed their accumulation over 12 hours).
I wrote those two paragraphs and then re-read your question and I wonder whether I have really answered what you were asking. Does the 6 hours of covering take place during the day and the 12 hours at night? In which case it sounds as though this plant is mainly a day-time nectar secreter so you should use those figures (assuming most of the visitors are during the day?)
Let me know if I've misunderstood!
Jeff
Hi Jeff; Yeah, the plants that I measured nectar were ornitophilus; I know that I have to compare the nectar rate within the same species. I covered them all night (12 hours) then, I collected the nectar in the morning (average of 10 microliters). I re-bagged the flowers (some did not produce any nectar, I do not consider them) and then measured again 6 hours later at mid-day, the average nectar volume was 35 microliters. So, should I use the 35 value and not the 10, because this plant secret more nectar during the day, and this is what is offered to its pollinators?
OK, when you said you were looking at a flower visitation "network" I assumed that you were studying more than one plant species and making comparisons between species. In any case, I would use the 35 microlitre values because the flowers that were bagged over night may have contained nectar from the previous day (unless you also collected the nectar from those before bagging?)
I do have measurements from several species, I gave the example of one species (Brachyotum lutescens), that behaved in that way. Other species, such as Tristerix longebracteatum, also show similar values in its nectar secretion. This is a high elevation forest (3800 masl) in the Andes. Maybe these differences in nectar secretion in the night and in the morning could be explained by the adaptation of these plants to keep their nectar reserves for the day, where their pollinators are active. Furthermore, in the night the temperature drops to freezing (0 Celsius). Would you agree?
Hi Jeff, Oscar and Deepu. I understand Jeff is seeking for a flower nectar parameter that would well correlate with the flower attractiveness to its visiting nectarivores. Well, this is not an easy goal. Measuring nectar volume is not enough, since in most cases the amount of sugars in the flower is the important parameter for the visitor. However, flower sugar amount (nectar volume multiplied by sugars concentration) is also not enough, since in many cases the visitor can't reach the whole nectar amount during a single visit. Nevertheless, even the available sugar amount (for a single visit) is not a good enough comparable measure, since the time demanded for the nectar collection is relevant as well. For instance, for comparing nectar attractiveness of sunflower bloom to Salvia flowers, it is not clear what one should measure in the sunflower head: the nectar of a single flower? The nectar of a one min visited flowers? Now, while comparing nectar attractiveness of a different plant species I only compare plants that are visited by the same nectarivore species. The parameter I've used for comparison was the amount of sugar (weight) that a nectarivore collects per min from the plant species flowers. I found this parameter to show a high correlation with the plant attractiveness. For measuring this parameter one should work on open flowers. a. Follow a nectarivore specimen and determine the number flowers it visits per min. Make at least 10 counts for that. b. Collect nectar from open flowers (at least 20, and expect a high variance), and measure its sugar containment. While choosing flowers for nectar collecting, try to imitate the nectarivore behavior. c. Calculate the amount of sugar a nectarivore collects per min by multiplying the average sugar amount per flower by the number of visited flowers per min.
Hi dears, i think this code is useful:
Flower Pollination Algorithm
This matlab demo code shows how to use the new flower algorithm to solve unconstrained global optimization problems.
Required Products
MATLAB 7.14 (R2012a)
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