Honeybees visiting the flowers of an invasive alien cactus

The Golden Torch cactus (Echinopsis spachiana) is native to South America (Argentina and Bolivia) and is classified as a Category 1 invasive alien plant in South Africa (Conservation of Agricultural Resources Act, 1983 (Act No 43 of 1983) (CARA)).  Category 1 plants are declared weeds and may not be planted or propagated.  Trade of the seeds, cuttings or other plant material used to propagate these plants are prohibited. They may not be transported or be allowed to disperse.  Although South Africa hosts a large diversity of succulent plants, species of the family Cactaceae (spiny succulents) are not native to South Africa (geen kaktus plante is inheems tot Suid-Afrika nie).  The only time this plant is appealing to the eye (according to me) is when it blooms; it produces large and beautiful white flowers.

There are several small patches where the Golden Torch cactus (Orrelkaktus in mooi Afrikaans) has become naturalized in the veldt around De Rust.  These plants started flowering in late November 2011 and are still continuing to flower.  The plants flower in bursts and our neighbour believes that when they flower it is a sign that it is going to rain.  The big and showy flowers have a noticeably strong sweet sent and only lasts for a few days.

Where this cactus is native it could be pollinated by either bats, hummingbirds, moths or bees – common pollinating agents of other cactus species.  The flowers of the Golden Torch cactus is nocturnal (flowering during the evening) just like many other cactus species.  I’ve done a literature search on the pollination of the Golden Torch cactus but did not find any scientific papers on the subject.

Photo from:  http://www.learner.org/jnorth/tm/spring/Bats_PollenProtein.html  A bat visiting the flower of a different cactus species.

Here in the Klein Karoo, honeybees visit the flowers and particularly collect pollen from the stamens, for their pollen baskets are loaded with pollen.

The style is the thicker protrusion in the middle of the flower, splitting up into many ends.  There are numerous stamens from which the honeybees collect the pollen.

It is not clear whether honeybees would be agents in the spread of this alien invasive weed by pollinating the flowers, unless their pollen dusted bodies come in contact with the stigmas of the flowers. 

No biological control agent has been released in South Africa for this invasive weed species.  The plants are apparently sensitive to frost.

The pollinator of a novel Pelargonium species growing near De Rust

Yesterday during a  walk in the veldt, I stumbled upon a pleasant surprise, and today, I’ve been treated even more.  I came across the most beautiful small Pelargonium (family: Geraniaceae) flowers I’ve ever seen.  They have an unusual cream colour.  Back at home I consulted my copy of Jan and Anne Lise Vlok’s book, “Plants of the Klein Karoo”.  Low and behold, this species is novel and does not even have a proper species name yet!  And the population I came across is the only one known of!!  Wow!! 

And to my delight, the pollinator of the flowers decided to show up when I went back this morning to take some pictures.  Luckily I managed to catch, what I think is a needle nosed fly (family: Tabanidae), in action, with my camera just wanting do to it’s own thing and miss behaving when I need it the most.  The other possibility is that this is a long-tongued fly (relatively rare), which I will only know for sure if I have it identified by an expert.

Unfortunately the fly and the flower it visits are out of focus in the next picture.  But if you look carefully, you’ll see the length of the fly’s tongue as it hovers over the flower in the distance.

Here is a specimen of the fly species I caught in August 2011 while it foraged on Jamesbrittenia tortuosa (family: Scrophulariaceae).

The Hybrid Onion Seed Production Region of South Africa

Hybrid onion seed are produced mainly in the Klein Karoo and partly in some areas in the greater Karoo in the Western Cape province.  The seed companies are mostly situated in Oudtshoorn.

The Klein Karoo is a longitudinal area of about 23 500 km² situated between two mountain ranges parallel to the southern coastal shores of South Africa (the Langeberg-Outeniqua mountain range in the south and the Witteberg-Swartberg mountain range in the north).  The soils of the lowlands are generally clayey and nutrient-rich while the mountains typically have sandy, nutrient-poor soils.  Soil surfaces in the lowland areas are dependent on a living soil crust, formed by small organisms like lichens, mosses, fungi and bacteria, to insure water infiltration, erosion control and nutrient cycling.  The Klein Karoo has a semi-desert climate with higher rainfall in the mountainous areas.  The diversity of environmental factors merging in the Klein Karoo is the reason for the very rich plant diversity.  About 3 200 plants have been identified in the region with 400 of them being endemic to the region.  Four vegetation types are recognized namely, subtropical thicket, succulent karoo, transitional shrubland and fynbos (Vlok & Schutte-Vlok, 2010).

Two of the four vegetation types found within the Klein Karoo, the fynbos and succulent karoo vegetation types, form part of two of the world’s 34 biodiversity hotspots (the Cape Floristic Region and Succulent Karoo).  The Cape Floristic Region is home to the greatest non-tropical concentration of higher plant species in the world.  (Ref: http://www.biodiversityhotspots.org/xp/hotspots/cape_floristic/Pages/default.aspx)  While the Succulent Karoo boasts the richest succulent flora on earth.  (Ref: http://www.biodiversityhotspots.org/xp/hotspots/karoo/Pages/default.aspx)

The ecosystems in the mountain ranges, which also serve as water catchment areas, are largely protected and unaltered in protected areas.  However, the lowland landscapes have been altered considerably over the years by agricultural practices.  One of the main farming practices in the region is ostrich farming that started between 1857 and 1860, which also impelled the cultivation of lucerne as ostrich fodder (Beyleveld, 1967). 

Ostrich farming in the Klein Karoo, near Calitzdorp

The topology of the Klein Karoo landscape where hybrid onion seed are produced, is largely characterized by undulating hills interchanged with historical floodplains along rivers and streams.  These floodplain areas is suitable for crop cultivation, while the hilly areas are mostly used for livestock grazing.

View of the Swartberg mountain range from the Klein Karoo, showing the hilly landscape in the foreground with a historical riverine floodplain in between.

Not much work has been done on the insect diversity found in the Klein Karoo.  Some work has been done on the occurrence and diversity of pollen wasps in the region and elsewhere by Fred and Sarah Gess from the Albany Museum in Grahamstown.  But the area remains largely under-sampled in terms of insect, and especially pollinator insect diversity, says Jonathan Colville, my promoter and entomologist at SANBI.  Thus, my work will be a valuable contribution to the knowledge base of pollinator insect diversity and distribution within the area covered in the study.  

Even the casual collection of insects can bring about new species being discovered.  Jonathan is particularly interested in monkey beetles, members of the family Scarabaeidae, which are largely endemic to southern Africa and important pollinators of many flowers.  He asked me to be on the look-out for them and collect them if I find some.  So, while we were busy data capturing on a site in the greater Karoo, a rather large monkey beetle came landing on the ground in front of me.  I picked it up, and pickled it in some alcohol.  It turned out to be a new species!  Needless to say, the monkey beetle specialists were ecstatic about the new discovery.  The trick is to be on the right place at the right time.

Biota: The Biodiversity Database Manager

Biota: The Biodiversity Database Manager:

'via Blog this'

How my research fits into the Bigger Picture

My research forms just a small part of the Global Pollination Project (GPP) run by the Global Environment Facility (GEF), who fund several projects undertaken in seven partner countries: Brazil, Ghana, India, Kenya, Nepal, Pakistan and South Africa.  The GPP is implemented through the United Nations Environmental Programme (UNEP) and executed by the Food and Agriculture Organization of the United Nations (FAO).

In South Africa, the GPP is being implemented by SANBI’s Applied Biodiversity Research Division based in Cape Town.  Several pollination projects have been initiated in South Africa and will run during a 5 year period from 2009 until the end of 2013.  The projects focus specifically on the pollination of agricultural crops and three crop types were chosen for the South African projects:

          1.  Appels (near Elgin & Ceres, Western Cape)
          2.  Onion seed (near Oudtshoorn, Western Cape)
          3.  Sunflower seed (near Bela-Bela, Northern Province)
These crops are dependent on animal pollination for successful production and quality produce.

I work on the onion seed pollination project.  The project specifically focuses on hybrid onion seed, where the bisexual flowers of the “male” parent plants produce pollen, and are crossed with “female” plants whose bisexual flowers do not produce pollen.  This out-crossing insures the production of sterile seeds.  The carrying of pollen from the “male” flowers in one row, to the “female” flowers in the next row, are solely done by insect visitors to the flowers.  Therefore, hybrid onion seed growers are totally dependent on the work done by honeybees and other insects.  If the honeybees do not visit the onion flowers, the crop will fail to produce any seed.

Picture 1: This crop of a hybrid onion seed cultivar clearly illustrates the commonly used planting formation of male-fertile and male-sterile rows of onion plants.  The male-fertiel rows in this example are a lighter, greyish green and are planted on the sides and in the middle of each section.  The difference between 'male' and 'female' rows are not always very obvious.

Onion crops are very labour intensive to produce and require large amounts of inset costs, but successful crops are highly profitable.  Seed growers need to overcome several challenges in producing a successful crop.  Onion plants are considerably susceptible to fungal and bacterial diseases, therefore they grow best in dryer climates.  Onions are also targeted by thrips, especially in drought years, and considerable amounts of pesticides are used to control pests and pathogens.  However, during flowering, no pesticides are sprayed to ensure the survival of pollinator insects and their attraction to the crop.  They’ve got an important job to do.

My job is to find out who the visitors to the flowering hybrid onion seed crops are, how abundant they are, where they come from, and how efficient they are in pollinating the crops (just to put it simply).  Because pollination is so crucial to successful hybrid onion seed production, most seed growers are not taking any chances and stock the crops with up to 10 honeybee hives per hectare to try to ensure adequate pollination.  The largest seed crop I’ve work on was about 6 hectares which was surrounded by 59 active honeybee hives (Pictures 2&3).

Picture 2:  The 6 hectare hybrid onion seed crop in the great Karoo near Laingsburg, stocked with 59 hives (visible as small squares around the field)

Picture 3:  The same field, from a distance

 You might think to yourself now: “Hey, but you know who’s doing the work then, the honeybees off course.”  And you are right.  Honeybees, according to me, do most of the work.  But it becomes more complicated than that.  The honeybee is in indigenous species in South Africa and is the most abundant wild pollinator in our ecosystems.  Therefore, here in South Africa and elsewhere where the honeybee is an indigenous species, we differentiate between two different types of honeybees based on the source from where they provide services to agricultural production.  Managed honeybee colonies, housed in the commonly used Langstroth hive, is an economic service supplied by beekeepers to several agricultural producers like seed growers.  While wild honeybees living in the environment supplies an ecosystem service to seed growers when they visit and pollinate their crops.  All the wild (not managed) insects visiting and pollinating agricultural crops are supplying an ecosystem service to farmers.  The cost to rent a hive of honeybees to pollinate your crop was between R250 and R270 per hive in 2010.  While the pollination services provided by insects from the ecosystem is totally free!  Even though they supply a very valuable service to our food production!

The GEF research projects' main focus is to determine the amount of pollination ecosystem services received by farmers in the participating countries, and to what extent the production of the selected crops are dependent on and/or improved by receiving these 'free' services.

Picture 4: A honeybee working on an onion umbel.

Images of male Xylocopa capitata bees

Xylocopa bees (family: Apidae) or alternatively known as carpenter bees (Afrikaans: Houtkapperby) make their nests in dead wood.

This male X. capitata are foraging on an Aizoaceae species.  The two white spots (white hairs) on the dorso-lateral regions of tergum 1 of the abdomen (also called the metasoma) are distinctive of the males of this species.  The females are completely black.  This is a very large species with a body length greater than 3cm.  

The yellow face-markings of the male is clearly visible in this photo.  The female has no coloured face markings.

Male X. capitata individuals regularly claim territories around Nymania capensis (Chinese lantern bush) individuals.  It is not uncommon to walk past one of these bushes when in flower and/or carrying seeds (late August into September), and being investigated by the resident X. capitata male.