Ant-aphid mutualism

Phloem sap is a nutrient-rich resource that is of less chemical defense. However, the phloem sap is not widely exploited because it is not easily accessible, lack of essential amino acids and has a high osmotic potential (i.e. too concentrated) relative to the insect bodies (Corlett, 2009). Hemiptera, including aphids, is the major insect group that consumes the phloem sap, so-called sap-suckers. They have specialized mouthparts and excrete the excess sugar as 'honeydew'.

The honeydew excreted by the Hemiptera generally contains more amino acids as the sap being processed by the symbiotic micro-organisms inside the Hemiptera bodies (Corlett, 2009). The honeydew also has lower osmotic potential so it serves as a better food sources to other insects (Corlett, 2009). Ants have established an obvious mutualism with aphids as they harvest the honeydew whilst protecting the aphids from their predators, parasites and pathogens in the meantime.

I have observed this interesting mutualism on the plant Goniothalamus tapisoides where the whole plant individual was covered with these aggressive weaver ants. It is interesting to know if a 'triple alliance' is present as the plant is also benefited as the ants protect the plant from other herbivores, which can probably compensate the loss of phloem sap (Moog et al., 2005).

The weaver ant harvesting the 'honeydew' excreted by the aphid. 

This ant is guarding the aphids on the inflorescence and waiting for the honeydew production. 

References:

Corlett, R.T. 2009. The ecology of tropical East Asia. Oxford University Press, Oxford, UK.

Moog, J., Saw, L.G., Hashim, R. and Maschwitz, U. 2005. The triple alliance: how a plant-ant, living in an ant-plant, acquires the third partner, a scale insect. Insectes Sociaux 52: 169-176.

Carex canina

Carex canina (Cyperaceae) is a highly restricted species which is only found in a few places in Guangdong, China including Hong Kong. It is therefore an endemic to Guangdong province. Nevertheless, it is not common at all in these localities where in the case of Hong Kong, Sunset Peak is the only locality where C. canina could be found.

Carex phacota

Carex phacota is one of the 20-odd Carex species (Cyperaceae) in Hong Kong. It was assessed to be very rare without recent specimens. However several localities have been found recently because of more nature lovers getting interest in the diversity of local flora.

Chlorophytum laxum

Chlorophytum laxum (Liliaceae) is an inconspicuous herbaceous species found in grassland or forest edge in Hong Kong. It was listed as having restricted distribution in Hong Kong. Fruits are remarkable as the capsules are acutely three-angled.

Manglietia cf. yuyuanensis

In a hiking trip in late June 2010, an atypical Manglietia species was found in a montane valley. We quickly recognized that it was not Manglietia fordiana, the only Manglietia species recorded in Hong Kong, as it has much smaller flowers than M. fordiana. It was thought to be another "taxon" no matter what taxonomic difference it refers to.

Magnoliaceae is indeed very well documented in China as they have very high ornamental and cultural value in the country. In the book "Magnolias of China", several small-flowered Manglietia were identified but the species matches only one of them, Manglietia yuyuanensis, which also has a geographic range close to Hong Kong. However, different taxonomists have different opinions on whether Manglietia yuyuanensis should be included in Manglietia fordiana. However, besides the morphological difference, we also noticed there is a difference of their flowering time which makes natural inter-breeding very unlikely to happen. Possibility of natural inter-breeding is conventionally an important criteria in taxonomy so this supports that they are at least of subspecies or variety level difference rather than a simple inclusion.

Yesterday we managed to make another trip to the valley to search for fruits but none was found. However, it is still exciting as more individuals were found. Many of them were adult tree but sapling or seedling were absent, suggesting that its regeneration is poor.

Black Rhinoceros

There are currently five extant species of Rhinoceros in the world. White Rhinoceros and Black Rhinoceros are recognized as African Rhinos while Indian Rhinoceros (or Greater One-horned Rhinoceros), Javan Rhinoceros and Sumatran Rhinoceros are the Asian Rhinos. Among them, Black, Javan and Sumatran Rhinos are categorised as critically endangered according to the IUCN Redlist. Javan Rhino is particularly rare, maybe one of the rarest animals in the world, that less than a hundred is left on the planet. There are two disjunct populations of them in which 28-56 individuals are estimated in Ujung Kulon National Park, Java, Indonesia and no more than 8 individuals in Cat Tien National Park, Vietnam (WWF, 2010).

The species shown here is Black Rhinoceros (Diceros bicornis) taken in Masai Mara national park, Kenya in 2009. The reserve together with the neighbouring Serengeti national park form one of the major unfenced areas for the Rhinoceros to live in. A recent study conducted a census by aerial reconnaissance surveys and estimated that there are about 461 individuals in these two nature reserves (Metzger et al., 2007). As a whole, IUCN SSC African Rhino Specialist Group (2008) estimated that there are a total of 4180 wild individuals in 2007 and the population trend is kept increasing.

Black Rhinoceros has once been very abundant but its number dropped drastically between 1970 and 1992 by 96% due to illegal hunting (WWF, 2010)! Demands from Middle East for ornamental uses and Asian countries for traditional medicines are the major threats to the species (that is also why the Asian Rhinos are particularly endangered). Warfare among the African countries makes its conservation difficult too.

Black Rhinoceros are indeed very susceptible to poaching as they are not only huge, but also due to their preference on habitats. They mainly inhabit and forage in grasslands and savannas which normally do not hide themselves in forests or other kind of shelters. They sometimes form group of up to 12 individuals which makes them easy to be killed off too.

I was lucky enough to see a mother with her calf wandering in the savanna in Masai Mara national park. Though I was so excited of seeing these rare magnificent animals in the wild, I was so worried of their fate in the meantime as illegal poaching is still serious in Africa.

"How are they?" I am thinking.

Good luck!

Reference:

IUCN SSC African Rhino Specialist Group. 2008. Diceros bicornis. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. <http://www.iucnredlist.org/>. Downloaded on 23 December 2010.
Metzger, K.L., A.R.E. Sinclair, K.L.I. Campbell, R. Hilborn, J.G.C. Hopcraft, S.A.R. Mduma and R.M. Reich. 2007. Using historical data to establish baselines for conservation: The black rhinoceros (Diceros bicornis) of the Serengeti as a case study. Biological Conservation 139: 358-374.
WWF. 2010. Rhinoceros. Available at <http://wwf.panda.org/what_we_do/endangered_species/rhinoceros/> Accessed on 23rd December 2010.

Balanophora fungosa

Genus Balanophora is belonging to angiosperms (flowering plants) though it is always misidentified as some kinds of fungi by hikers. Though it resembles fungi by appearance but you could find floral structures in Balanophora such as its staminate and pistillate flowers and bracts by close observation. Also, fungi is saprophytic while Balanophora is obligate parasitic with specific hosts.

The specimen shown here is Balanophora fungosa taken in Queensland in late Oct, 2010. It actually has a wide distribution which is ranged from Northeastern Australia, Pacific Islands, East Malaysia, India, Taiwan and South Japan. It was reported having various hosts including Macaranga tanarius and Diospyros philippensis etc (Hsiao et al., 2010). It has monoecious inflorescence where pistillate flowers are on the upper part of the inflorescence while staminate flowers are on the lower part. There is also a wide range of floral color where the populations from Taiwan and Japan are pinkish orange while those in Queensland are yellow, as shown in the photographs here. Though it is considered as rare and vulnerable in Taiwan but it was found very abundant on the forest ground in Queensland, maybe due to different climate and host availability.


Reference:
Hsiao, S., W. Huang and L. Maw-Sun (2010). Genetic diversity of Balanophora fungosa and its conservation in Taiwan. Botanical Studies 51: 217-222.