Seasonality of Leaf and Fig Production in Ficus squamosa, a Fig Tree with Seeds Dispersed by Water

The phenology of plants reflects selection generated by seasonal climatic factors and interactions with other plants and animals, within constraints imposed by their phylogenetic history. Fig trees (Ficus) need to produce figs year-round to support their short-lived fig wasp pollinators, but this requirement is partially de-coupled in dioecious species, where female trees only develop seeds, not pollinator offspring. This allows female trees to concentrate seed production at more favorable times of the year. Ficus squamosa is a riparian species whose dispersal is mainly by water, rather than animals. Seeds can float and travel in long distances. We recorded the leaf and reproductive phenology of 174 individuals for three years in Chiang Mai, Northern Thailand. New leaves were produced throughout the year. Fig production occurred year-round, but with large seasonal variations that correlated with temperature and rainfall. Female and male trees initiated maximal fig crops at different times, with production in female trees confined mainly to the rainy season and male figs concentrating fig production in the preceding months, but also often bearing figs continually. Ficus squamosa concentrates seed production by female plants at times when water levels are high, favouring dispersal by water, and asynchronous flowering within male trees allow fig wasps to cycle there, providing them with potential benefits by maintaining pollinators for times when female figs become available to pollinate

Riparian Ficus tree communities: the distribution and abundance of riparian fig trees in northern Thailand.

Fig trees (Ficus) are often ecologically significant keystone species because they sustain populations of the many seed-dispersing animals that feed on their fruits. They are prominent components of riparian zones where they may also contribute to bank stability as well as supporting associated animals. The diversity and distributions of riparian fig trees in deciduous and evergreen forests in Chiang Mai Province, Northern Thailand were investigated in 2010-2012. To record the diversity and abundance of riparian fig trees, we (1) calculated stem density, species richness, and diversity indices in 20×50 m randomly selected quadrats along four streams and (2) measured the distances of individual trees from four streams to determine if species exhibit distinct distribution patterns within riparian zones. A total of 1169 individuals (from c. 4 ha) were recorded in the quadrats, representing 33 Ficus species (13 monoecious and 20 dioecious) from six sub-genera and about 70% of all the species recorded from northern Thailand. All 33 species had at least some stems in close proximity to the streams, but they varied in their typical proximity, with F. squamosa Roxb. and F. ischnopoda Miq the most strictly stream-side species. The riparian forests in Northern Thailand support a rich diversity and high density of Ficus species and our results emphasise the importance of fig tree within the broader priorities of riparian area conservation. Plans to maintain or restore properly functioning riparian forests need to take into account their significance

Mean number of figs, crop sizes, asynchrony, stem diameter, height and crown diameter per tree in each site over the study period.

<p>Mean number of figs, crop sizes, asynchrony, stem diameter, height and crown diameter per tree in each site over the study period.</p

Bar graphs show the mean values and the standard deviations for each of the variables that showed statistically significant differences between study sites (MK, PDN, MS, and MSN).

<p>Different upper case letters on the bars represent significant differences among the means when Kruskal-Wallis and Mann-Whitney <i>U</i>-test.</p

Differences in fig tree mean species richness and density in different river distance bands (four study sites combined).

<p>Differences in fig tree mean species richness and density in different river distance bands (four study sites combined).</p

Spearman rank non-parametric bivariate correlation between number of crops and crop size with stem diameter, height and crown diameter in each site and sex.

<p>Spearman rank non-parametric bivariate correlation between number of crops and crop size with stem diameter, height and crown diameter in each site and sex.</p

Stem abundance (A) and species richness (B) at four study sites: (HK) Huay Kaew stream, (MKL) Mae Klang stream, Mae Sa (MS) stream and Mae Ka stream (MK).

<p>Stem abundance (A) and species richness (B) at four study sites: (HK) Huay Kaew stream, (MKL) Mae Klang stream, Mae Sa (MS) stream and Mae Ka stream (MK).</p

Mean number of stems (A, C) and mean number of species (B, D) in four stream sites (left) and at each stream distance stratum (right).

<p>The boxplots describe the relationship between mean number of stems and species richness in each stream and stream distance strata. The maximum and minimum extents of the boxes indicate 25th and 75th percentiles and thick solid lines indicate the medians.</p

Correlations between phenological and abiotic factors in different <i>Ficus squamosa</i> populations.

<p>Correlations between phenological and abiotic factors in different <i>Ficus squamosa</i> populations.</p

Circular histograms, vectors and distributions of figs at different developmental phase (A-D) at four study sites.

<p>The vector represents the mean bearing and the arc outside the circle is the 99% confidence interval for the mean bearing.</p