The classification of secondary forests of Singapore: native-dominated secondary forests, abandoned land forests and waste-woodlands (Yee et al 2016)

Yee, A. T. K., K. Y. Chong, L. Neo & H. T. W. Tan, 2016). Updating the classification system for the secondary forests of Singapore. Raffles Bulletin of Zoology Supplement No. 32: 11-21 [pdf].

In this paper, the authors examine dryland secondary forests of Singapore with a defied tree canopy layer (i. e. not scrubland). They classify these secondary forests based on their land-use histories into three forest types:

  1. Native-dominated secondary forests – forests regrown on land cleared before the 1950s, and dominated by native tree species.
  2. Abandoned-land forests – forests regrown over abandoned plantations or kampungs, with mature trees largely intact.
  3. Waste-woodlands – forests regrown over land cleared usually after the 1960s, and dominated by exotic tree species. Species composition derived from seed source of the surroundings at the time of clearance, and succession. Reclaimed land forest (technically primary succession) is structurally similar to waste-woodlands with a species composition likely derived from the fill material.”

The authors remind us that land-use history of a single patch of secondary forest can be heterogeneous, and would require a mixed classification to best describe it.

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See also, Yee, A. T. K., R. T. Corlett, S. C. Liew & H. T. W. Tan, 2011. The vegetation of Singapore—an updated map. Gardens’ Bulletin Singapore, 63(1&2), 205-212 [pdf].

“Vegetation covers 56% of Singapore’s total land area: 27% is actively managed (parks, gardens, lawns, etc.) and 29% is spontaneous vegetation. Primary lowland dipterocarp forest and freshwater swamp forest cover only 0.28% and is confined to the Bukit Timah and Central Catchment Nature Reserves. The majority of the non-managed vegetation is secondary forest of various kinds, dominated by native or alien trees.”

Thu 19 Jan 2017: 10.00am @ DBS CR1– Nesibe Özsu on “The genetic basis of eyespot color pattern development in Bicyclus anynana butterflies”

Image004PhD Defense Seminar cum Oral Examination

The genetic basis of eyespot color pattern development in Bicyclus anynana butterflies

Speaker: Nesibe Özsu (Graduate Student Dept.of Biological Sciences, NUS)
Date: 19 January 2017, Thursday
Time: 10 am
Venue DBS Conference Room (S3 Level 5)
Supervisor: Assoc Prof Antonia Monteiro

All are welcome

Abstract – The origin of novel traits remains an outstanding question in evolutionary biology. In particular, it is largely unknown how these novel traits originate via modifications in development. Butterfly eyespots are complex novel traits that originated once, from simpler coloured spots, within the family Nymphalidae. Although several genes associated with eyespot development have been identified, the underlying gene regulatory network and function of eyespot genes still remains largely unknown.

Using a transcriptome analysis, I first identified 186 genes that were differentially expressed in wing tissues that develop eyespots in Bicyclus anynana compared to wing tissues that don’t. Many of these genes were involved in wound healing, suggesting that butterfly eyespots may have originated with the co-option of the wound healing gene regulatory network. Second, I investigated the genetic basis of eyespot number variation using an eyespot number mutant, Spotty, with two additional eyespots. Only a handful of the 461 genes that were differentially expressed between Spotty and wild-type butterflies overlapped with genes from the eyespot gene regulatory network, indicating possible targets for Spotty. Finally, I tested the function of wingless, a gene previously implicated in eyespot development, by down-regulating it in transgenic B. anynana butterflies via RNAi. Transgenic butterflies showed significant reductions in the size of eyespots and wings, compared to wild-type controls, indicating that wingless is a positive regulator of eyespot and wing development in B. anynana butterflies.

Fri 13 Jan 2017: 10.00am @ DBS CR1 – Mindy Tuan on “Comparative and experimental approaches to understanding sexual selection in Sepsidae (Diptera)”

Image004PhD Defense Seminar cum Oral Examination

“Comparative and experimental approaches to understanding sexual selection in Sepsidae (Diptera)”

Speaker: Tuan Jia Min Mindy
(Graduate Student, Dept. of Biological Sciences ,NUS)
Date: 13 January 2017, Friday
Time: 10 am
Venue: DBS Conference Room (S3 Level 5)
Supervisor: Professor Meier, Rudolf

All are welcome

Abstract – Natural history and discovery science has taken a back-seat as hypothesis-testing using model species has become a standard approach in biology. This is one reason why the vast majority of described species are severely data-deficient and very little is known is known about their behaviour, interactions with other species, and ecosystem functions. In my thesis, I explore the behavioural diversity within black scavenger flies (Diptera: Sepsidae) which have ca. 350 described species. Sepsidae include a few “model species” (e.g., Sepsis cynipsea, Sepsis punctum, and a few species of Themira, Archisepsis and Microsepsis), but little is known about the remaining taxa. In my thesis, I use a comparative approach to explore the behavioural diversity space of Sepsidae by studying the mating behaviour of 49 species and use comparative and experimental approaches to document and understand the behaviour.

I find that sepsids are one of the few insects that perform “sensory kissing”, which is significantly different from the nuptial kissing observed in other dipterans or the kissing performed by drosophilids to assess females’ receptivity before mating. Sepsids also evolved a variety of ways to terminate copulations. For example, some species use a novel “twisting” motion that allows the male to “pivot” clock- or anti-clockwise in order to separate from the female. Data analysis suggests that this new behaviour is adaptive because it allows for faster and more predictable separation times. Similarly variable is copulation time. The copulation time of sepsids varies 5 minutes to 5 hours and I show through ancestral state reconstruction and sensitivity analyses that copulation time undergoes considerable amounts of evolution. Furthermore, I used experimental reciprocal crosses between separated conspecific populations to determine which sex controls copulation duration. Experimental perfuming of females using osmeterium secretions from males were also performed to test whether the secretion possessed an anti-aphrodisiac function. Finally, I detailed the repertoire, action patterns and phases for 24 species of sepsids.

This work revealed interesting and rare behaviours, as well as widespread polymorphism within species, which would have remained hidden if only model species had been studied. This illustrates the importance of comparative research on the natural history of many species. It both broadens and deepens our knowledge of animal diversity.

Fri 13 Jan 2017: 2.00pm @ DBS CFR2 – Pang Sook Cheng on Distribution and bionomics of Anopheles sinensis, and its role of the malaria transmission in Singapore

Image003PhD Defense Seminar cum Oral Examination

Distribution and bionomics of Anopheles sinensis, and its role of the malaria transmission in Singapore

Speaker: Pang Sook Cheng
(Graduate Student Dept. of Biological Sciences, NUS)
Date: 13 January 2017, Friday
Time: 2pm
Venue: DBS Conference Room II (S1 Level 3, mezzanine)
Supervisor: Assoc Prof Li Daiqin

All are welcome

Abstract – Research on Anopheles mosquitoes has always been of low priority due to the malaria free status of Singapore since 1982. However, Anopheles sinensis were persistently found in localized malaria outbreaks in 2009 and kick started the investigation on the distribution, bionomics and the role of malaria transmission of this species. In this study, we confirmed the presence of A.sinensis Form A and the possible absence of Form B in Singapore.

Anopheles sinensis Form A was experimentally incriminated as a Plasmodium vivax vector and were found to be anthropophilic. Being the most widespread anopheline, they were present in a third of the total investigated sites and were actively seeking host throughout the night, especially before 1.00am. In the wild, their abundance positively correlative with the average and minimum temperature, but not rainfall.

Basic biological characteristics of A. sinensis were also pursue to further understand the fundamental knowledge to epidemiology of malaria. This study has revealed that A. sinensis could pose a malaria threat in urban Singapore, if the risks are not managed.

Painted Jezebels and relatives have deterred predators first with yellow, then red – Jocelyn Wee’s honours project with Antónia Monteiro published in PLoS

The Painted Jezebel is common sight around Singapore in both nature reserves and urbanised areas, including the NUS campus (see this post at Butterfly Circle). They are well recognised by the colours on their hindwings, the undersides of which bear bright yellow and red colours.

Sensing danger, most butterflies will fold and hold their wings over their body, exposing their undersides, i.e. ventral wing surfaces, during an attack. It is presumed that these colours advertise a butterfly’s unpleasant taste to predators, deterring attack. However, this has not actually been empirically demonstrated, even though the asgenus is a diverse one, ranging over South Asia and Australia.

Jezebel

Last year undergraduate Jocelyn Wee set out on her honours project with Antónia Monteiro to experimentally test is the colours of Delias hyparete function as aposematic signals.

To do this, Jocelyn constructed artificial paper models with a faithful colour representation of D. hyparete and a grey scale model. She also produced models with single colours intact, grey-scale models or models with no colours. All models were placed simultaneously in the field, with a live mealworm attached. The relative attack rates were measured on 100 models each at three separate field sites – Kent Ridge Road, Tampines Eco-Green and Jurong Eco Garden.

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Faithful models of D. hyparete suffered the least amount of attacks, followed by grey-scale models with unaltered red patches, and then by grey-scale models with unaltered yellow patches. They concluded that red and yellow colours function as warning signals.

Next, they mapped dorsal and ventral colouration onto the phylogeny of Delias. This revealed that yellow and red colours appear almost exclusively on the ventral wing surfaces. Basal lineages have mostly yellow, white, and black wings, whereas derived lineages contain red colour in addition to the other colours. Red appears to be, thus, a novel adaptive trait in this lineage of butterflies.

This work was published last week at PLoS as Wee, J. L. Q. & Monteiro, A., 2017. Yellow and the novel aposematic signal, red, protect Delias butterflies from predators. PloS one, 12(1), e0168243.

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