Nico's focal taxon

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Ficus; Moraceae

Ficus is a diverse and abundant genus of tropical woody plants in the family Moraceae. For a single genus, Ficus includes species with an unusually broad range of lifestyles and ecological niches - from small hemi-epiphytes to giant 'stranglers' to free living forest trees to montane and temperate varieties. Indeed, were it not for the unique reproductive strategy shared by all fig species, the individual members of Ficus would likely be grouped into multiple genera.[1] This reproductive strategy bears further discussion: the inside of a fig's fruit is lined tiny flowers which can only be pollinated from within the fig. This requires very tiny insect pollinators, and in fact every species of fig has a symbiotic relationship with a species of wasp that pollinates it. Moreover, fig wasps depend on their figs to reproduce; thus the relationship is one of two-way dependence. Fig/wasp interactions and life cycles are incredibly complex in their own right, and are made even more interesting by the many parasites and other organisms that also live and play a role in the habitat of the fig's interior. Despite science's long acquaintance with figs, the complexity of the reproductive ecology of Ficus continues to fascinate researchers and provide material for new publications. Other common features of figs include trivenate leaves (that is, leaves in which the first veinlet pair branching from the mid-vein makes a more acute angle with respect to the mid-vein than subsequent pairs), aerial or basketing roots (in hemi-epiphytes), and milky latex throughout the plant body.

Ficus species also play a keystone role in tropical ecosystems.[2] Because they fruit periodically throughout the year, their fruits are always available to local frugivorous animals, especially birds. Fig availability is especially important when other tropical trees are not fruiting, as figs may provide the only source of food for frugivores during such times. Thus Ficus is a genus particularly appropriate for taxonomic investigation.

Observations

Hemi-epiphites

Morphotype Code: HE1

Binomial: Ficus kerkhovenii

Location: Lambir Hills HQ

Observation: Indiv10

Notes: The pictured specimen was found in a deforested and heavily disturbed area alongside the road at Lambir Hill National Park HQ. It was in full fruit; an abundance of birds fed on its figs every morning. This morphotype has fruits and leaves of medium size, conspicuous tri-venation, and copious basketing roots. Its yellow-orange figs are sessile and located almost exclusively at the bases of its leaves. A second, smaller individual was found on the Maliau Basin Skybridge.

Morphotype Code: HE2

Binomial: Unknown

Location: Lambir Hills HQ

Observation: Indiv12

Notes: This agressive strangler was found in the Lambir Hills National Park HQ parking lot. It is particularly notable for its linear leaves - the only individual to have leaves of this shape. Unfortunately, it was not in fruit at the time of the observation, making it difficult to identify. This particular individual seemed to have an association with a colony of ants. Whether the association is purely coincidental or characteristic of the morphotype is a question open to investigation.

Morphotype Code: HE3

Binomial: Ficus microcarpa

Location: Pulau Gaya

Observation: Indiv4

Notes: This individual was found in a disturbed area near the beachside camp on Pulau Gaya. Though it is clearly a hemi-epiphyte, it had begun to grow near the base of a tree that had subsequently toppled and been submerged in a pool of water, giving it the impression of a free-living species. The morphotype has small elliptic leaves and gray bark.

Morphotype Code: HE4

Binomial: Ficus consociata

Location: Pulau Sapi

Observation: Indiv20

Notes: This morphotype, which was identified from two leaf specimens as F. consociata by Shawn Lum, was found on Pulau Sapi. It exhibits conspicuously trivenate leaves. Unfortunately, neither the fruit nor the body of the individual from which the leaves had fallen could be identified.

Morphotype Code: HE5

Binomial: Unknown

Location: Maliau Basin Skybridge

Observation: Indiv132

Notes: Morphotype HE5 differs from morphotype HE1 in that the former exhibits slightly elongated leaves with distinct tips, more numerous veinlet pairs branching from the midvein, and an absence of conspicuous tri-venation. This individual was found in the crotch of a tree on the Maliau Basin Skybridge.

Morphotype Code: HE6

Binomial: Unknown

Location: Maliau Basin

Observation: Indiv152

Notes: The one HE6 individual, which was found at the forest's edge along the trail leading away from the Maliau Basin Study Center, is notable for its broad, tipped leaves and numerous veinlet pairs. The fact that the observed individual was not fruiting precluded exhaustive character analysis.

Morphotype Code: HE7

Binomial: Unknown

Location: Maliau Basin

Observation: Indiv153

Notes: This towering strangler was observed at the forest's edge near the entrance to the Maliau Basin Study Center. Its figs are morphologically very similar to the figs of morphotype HE1, but the two morphotypes can be distinguished by patterns of leaf size, shape, and venation. The individual observed was in full fruit, and was filled with birds each morning.

Morphotype Code: HE8

Binomial: Unknown

Location: Maliau Basin

Observation: Indiv155

Notes: The massive leaves of morphotype HE8 were found during the four-day hike through Maliau Basin Conservation Area. Besides the clear difference in leaf size and number of veinlet pairs, this morphotype appears to be very similar to morphotype HE1; it has a similar leaf shape and the same conspicuous tri-venation. Unfortunately, the individual observed was not in fruit, so more extensive character information could not be collected.


Free-living trees

Morphotype Code: FT1

Binomial: Ficus fistulosa

Location: Lambir Hills HQ

Observation: Indiv11

Notes: This individual was found in a highly disturbed stand of secondary forest in a swampy area immediately next to the highway leading to Lambir Hills National Park. Geographical and botanical barriers precluded close observation, but nevertheless it was possible to determine enough to identify this morphotype as the ubiquitous F. fistulosa, a common free-living fig in disturbed areas across Borneo. This fig is chiefly interesting for the placement of its stalked fruits on its trunk in addition to its twigs and branches.

Morphotype Code: FT2

Binomial: Ficus olaefolia

Location: Mt. Kinabalu

Observation: Indiv23

Notes: var. myrsinoides

This shrubby montane fig species is notable for its minute leaves and figs. It was in full fruit at the time of observation, its ripe figs reaching a mature diameter of significantly less than one centimeter! Two individuals were found clumped on the trail up Mt. Kinabalu, at an elevation of around 1500m.

Morphotype Code: FT3

Binomial: Ficus endospermifolia

Location: Mt. Kinabalu

Observation: Indiv28

Notes: F. endospermifolia has broad cordate leaves and rather large, sessile figs that ripen to a greenish-yellow color. It is notable not only for its unusual leaf shape but also for the fact that its leaves and twigs are hairy - a character not observed in any of the hemi-epiphytic figs. This individual was observed in full fruit by the resthouse at Mt. Kinabalu HQ.

Morphotype Code: FT4

Binomial: Unknown

Location: Road to Maliau Basin

Observation: Indiv61

Notes: The only so-called earth-fig observed, this morphotype is unique in that it fruits on subterranean runners rather than on its trunk or twigs. It is also notable for its hairy leaves and branches and interesting frilled leaf shape, which is unlike any other morphotype observed. This individual was observed, not fruiting, at a turnout on the road to the Maliau Basin Conservation Area.

Morphotype Code: FT5

Binomial: Unknown

Location: Maliau Basin

Observation: Indiv154

Notes: This individual was found on our four-day hike through the Maliau Basin Conservation Area. It is especially notable for the large, stalked figs on its twigs and branches, the numerous veinlet pairs branching from its midvein, and its brown bark. It is one of only two morphotypes with stalked figs, both of which are free-living.

Morphotype Code: FT6

Binomial: Unknown

Location: Mt. Kinabalu HQ Trail

Observation: Indiv160

Notes: This unique morphotype was found in the area surrounding Mt. Kinabalu HQ. The many bumps and distortions of its leaf surface are distinctive. It was initially unclear whether the individual observed was a hemi-epiphyte or a free-living plant because it appeared to be growing out from under a fallen tree. However, closer observation suggested a free-living habit, and it was categorized correspondingly as a working hypothesis.

Analysis

Below is a table of the characters and states used to generate a phylogenetic tree of the fourteen Ficus morphotypes observed. Unknown character states are indicated by '?', and dependent states lacking an antecedent conditional by '-'.

This character matrix was used to generate a set of maximally parsimonious phylogenetic trees using the pars tree inference tool in the Phylip application package. A consensus tree was then created using Phylip's consense tool:

The nexus file encoding the character matrix used to generate the tree can be viewed by clicking the following link:

File:Nkg Focal.nex

The table below summarizes the sites at which each morphotype was observed:

Discussion

The consensus tree generated using Phylip shows several very interesting and informative patterns, which become more visible when the states of single characters are plotted back onto the original tree.

The most striking result of the morphometric analysis is likely the clustering of five of the six free-living morphotypes together within the hemi-epiphytic morphotypes. Since the hemi-epiphytic lifestyle likely requires numerous specific adaptations that differ from the adaptations required for independent growth, however, this close clustering and evolutionary conservation of lifestyle is not unexpected.

More interesting is the apparent association of bark color with lifestyle; with only a few exceptions, hemi-epiphytic morphotypes have light/grey bark, while free-living morphotypes have dark/brown bark. This finding, if it can be shown to be robust, immediately suggests further questions: Is the observed partitioning of bark color adaptive, or is it merely a trait that has been carried along with the speciation of the figs observed? And if the trait is adaptive, how does its effect work? The answer could have something to do with habitat specialization or fig-wasp interaction.

The presence of basketing roots seems to be primarily associated with a closely-related subgroup of the hemi-epiphytic morphotypes included in the study. The tree produced by Phylip makes this subgroup appear basal to the rest of the genus; however, the tree is unrooted, and it seems prima facie more likely that the basketing trait is derived rather than basal. Nevertheless, it is interesting that the presence of basketing roots is so localized on the tree.

Finally, note that higher-elevation morphotypes are clustered together into a single clade. If this result proves robust, it also tells an interesting story about Ficus. In particular, the relatedness of high-elevation species suggests a single high-elevation colonization event followed by an adaptive radiation, rather than multiple colonizations by less closely related taxa. Such a pattern would be in keeping with recent findings about high-altitude birds, which suggest relatively few colonization events followed by broad mountain-to-mountain dispersal.

References

  1. C. Berg. Classification and distribution of ficus. Cellular and Molecular Life Sciences, 45(7):605–611, July 1989.
  2. F. Lambert and A. Marshall. Keystone characteristics of bird-dispersed ficus in a malaysian lowland rain forest. The Journal of Ecology, pages 793–809, 1991.


Individual Determined by Date Taxon Genus Species Morphotype
Indiv10 Kinari 11 June 2010 Ficus Ficus
Indiv10 Nico 18 June 2010 Ficus kerkhovenii Ficus kerkhovenii
Indiv11 Nico 18 June 2010 Ficus fistulosa Ficus fistulosa
Indiv11 Doni 13 June 2010 Ficus Ficus
Indiv12 Nico 13 June 2010 Ficus Ficus HE2
Indiv132 Nico 6 July 2010 Ficus Ficus HE5
Indiv152 Nico 2 July 2010 Ficus Ficus HE6
Indiv153 Cam 27 June 2010 Ficus Ficus HE7
Indiv154 Nico 4 July 2010 Ficus Ficus FT5
Indiv155 Nico 4 July 2010 Ficus Ficus HE8
Indiv160 Shawn 21 June 2010 Ficus Ficus FT6
Indiv20 Shawn 19 June 2010 Ficus consociata Ficus consociata
Indiv23 Nico 29 June 2010 Ficus olaefolia Ficus olaefolia
Indiv28 Nico 29 June 2010 Ficus endospermifolia Ficus endospermifolia
Indiv4 Shawn 16 June 2010 Ficus microcarpa Ficus microcarpa
Indiv61 Cam 26 June 2010 Ficus Ficus FT4