July 11, 2024

Oxalis Genus: plasticity of form (single taxon)

Oxalis luteola [attached observation]

  • Thicker and more stout conjunction of rootstock and basal leaf buds
  • Underground tuber somewhat wedged under the packed stones in hard ground
  • Pillose hairs on leaf underside, with scatterings on margin (UV diffusion from sunlight stones?)
    = Adapted for stability and midday sun exposure in shallow, stony soil. No abnormal length in flowering stem

Oxalis luteola [not posted]

  • seen growing in marshier habitat, with seasonally waterlogged soil and amongst lush vegetation of uniform height
  • No telling adaptation with conjunction of stem and leaf bases, no longer truly basal but held aloft with longer petioles
  • No visible hairs on leaf underside
  • No seeming difference with tuber orientation, but tubers slightly smaller?
    = Adapted to compete with densely growing, higher canopy vegetation for consistent pollinator attraction and associated dispersal - flowering stem >30cm long!

Q: What causes this plasticity in a single species? Moisture saturation of seedlings and length of said exposure? Light/shade differences in growing environment for newly sprouted seedling?
Q: How did this species or greater taxon (Oxalis) come to be so adaptable to very different growing conditions?
Perhaps other associated neo-endemic species with maximum genetic vitality displaying similar plasticity?

Posted on July 11, 2024 12:31 AM by anthonywalton anthonywalton | 1 observation | 0 comments | Leave a comment

March 25, 2024

Dalechampia capensis: Species complex?

Ob 1: -Primarily near-ground sprawler
-3rd lobe set mostly cryptic (leaves)
-Leaf lobes not depressed
Ob 2: -Primarily arboreal
-3rd lobe set mostly well-defined
-Ocassional die-back, with signs of altered growth along latter nodes
Ob 3: -Mixed Habit
-Leaf lobes depressed toward palm centre
-Many leaves with glossy leaf surface, elucid leaf veins with clear star formation

Changes explained entirely by shifting conditions from season to season, or..?

Posted on March 25, 2024 04:40 PM by anthonywalton anthonywalton | 3 observations | 0 comments | Leave a comment

October 27, 2023

Forest Elephants in South Africa's Southern Cape: A naturally adapted or man-induced occupation?

I know there is a school of thought prevalent in mammal conservation circles which suggests that forest-inhabiting Elephants in the Southern Cape are just relics of evasive behaviours of herds centuries ago which tried to take shelter from the onslaught of European hunters, and that regardless of how long they've spent in the forest, they aren't tied to it in any important ecological sense. I've long agreed with such a view as amongst other things, it goes a long way in explaining why re-introductions from Kruger have failed.
This book however, really challenges this thinking on many fronts
Some things I didn't know before reading this book:

  1. The forests in the Garden Route impart a distinct mineral profile in Elephant diet. Namely, they are very low in Phosphorous, which causes an increase in pre-natal calf deaths and reduced calf/adult life spans; and they provide excess Calcium, which afflicts digestion of certain food sources and further inhibits intake of Phosphorous and other nutrients, stunting growth.
  2. Elephants in this area had been encountered well before even the founding of George in 1811, and were frequently encountered by travellers on the road to Knysna and further still to Plettenberg Bay. Many people recorded that these Elephants spent more of their time in the Fynbos and grassland patches inbetween forests when first encountered, but spent enough time traversing through and foraging in forests so as to leave a network of established trails that even the first loggers in the area came to frequent and turn into roads for wagons. As people began to settle the grassland areas for farming, the Elephants would spend more time in the Fynbos and forests, but this is inferred to be a pattern of behaviour that began even before the arrival of the first Europeans and may have already started with the centuries old impact of veld fires that the San and Khoikhoi groups would set to flush out game.
  3. The plight of the forest Elephants was already a concern in the late 1800's and as far back as 1908, they were declared Royal Game by the Crown Colony and hunting was tightly restricted. In the preceding 40 or so years before this declaration was made, their numbers had dropped from around 500 to just 20! This was owed to alot of unfortunate happenstance in the region which saw great influxes of people and inevitably hunters, such as the gold rush of Millwood and the demand for wagon wood at the outset of the Great Trek. The region became so full of people at one point that it is still suspected that many loggers at the time were incentivized to destroy Elephants on sight and smuggle their tusks to the Transvaal to get in on the illicit but highly profitable ivory trade.
  4. In 1968, when there were only a mere 12-14 Elephants remaining in the most remote sections of these Forests, a survey was commissioned by the then Department of Nature Conservation into the mechanisms of elephant survival and fecundity in the Garden Route forests. The results were that these Elephants selected certain tree and plant species in the forests which through inherited experience, they had come to identify as the most palatable and nutritious such as Cape Beech and certain parts of the Keurboom (Virgillia oroboides). Furthermore, though their population only grew very slowly even in the absence of poaching and habitat loss, they were in effect still able to breed normally and produce reproductively viable offspring in these forest environments.

CONCLUSION
With these insights foremost in our minds, surely there is room to ponder the real relationship between Afrotemperate forests and the Elephants? Though 14 Elephants is not the greatest study sample one could have, could it be that grassland Elephants had an innate, natural response to climatic stresses in their normal habitats that was expressed as a collectivized retreat and residence in our temperate forests? Maybe what we think to be an artificially, man-induced behaviour isn't after all? Could the Knysna Elephant's occupation of closed canopy forests represent a shift in reproductive strategy towards delayed fertility and smaller output in exchange for more reliable recruitment, particularly in an episode of environmental stress?

Posted on October 27, 2023 02:07 PM by anthonywalton anthonywalton | 0 comments | Leave a comment

July 16, 2023

White Rhino fungal innoculation through dung deposits

If I were to recall my observations of White Rhino dung in the field against dung from other large/r herbivorous mammals, I could cautiously conclude that:

  1. White Rhino dung has far better moisture retention (i.e. stays wet for far longer) than the dung of Equids, Bovids, or even Elephants - water being a critical conduit through which fungal mycidia are stored and expand from a host
  2. White Rhino dung is far more likely to bear fungal fruiting bodies than dung of the above-mentioned animals

Hypothesis: White Rhino innoculate patchwork areas of grassland/ Savannah ground by depositing dung conditioned for the harbouring and enhancement of fungal hyphae through conidia eaten on grass bodies. This innoculation is consistent with the Euclidean movement patterns of large grazers and thus occurs on a broader spatial scale owing to extended digestion times.

Posted on July 16, 2023 09:56 PM by anthonywalton anthonywalton | 0 comments | Leave a comment

November 04, 2022

Gerbera ambigua

var. -[Golden Gate]

Has wiry, untaut, pubescent hairs on lowerside petiole base, degree of hair concentration may vary
Upperside leaf texture may also vary
Inflorescence stalk commonly with villose stubble

Posted on November 04, 2022 10:09 PM by anthonywalton anthonywalton | 0 comments | Leave a comment

Jamesbrittenia pristisepala

Unique features:

Yellow-purple tube mouth + bladder-like hairs on short based sepals

/shrub

Posted on November 04, 2022 10:01 PM by anthonywalton anthonywalton | 0 comments | Leave a comment

October 29, 2022

In-Field Observations of Chacma Baboon (Papio ursinus) Troop in southern limits of Golden Gate Highlands National Park

Diet

Leaf culms:
=Xerophyta sp.
=Poaceae FAMILY (e.g Aristida sp.)

Inflorescences:
=Scila natalensis (bitten off with incissors 3-8cm above the stalk base)
<> Bulb of S. natalensis very toxic to humans, toxins can be found in early growth flower stalks
anecdotal evidence of olfactory adaptations of Chacma Baboon to distinguish between
accumulations and absence of digestive inhibitors in differentiated plant tissue
[refer also to mechanical removal of Watsonia culms in the Cape region]

Behaviour
1.
<>Early oestrus females consorting with young, low-ranking males, give a post-copulatory vocalization differing in pitch and frequency to conspecifics in Western Cape and Cape Peninsula
<> Many possible explanations for vocalization difference: e.g. necessitated acoustic change in response to varied topography, changes in ambient range dependant on time of day as the 2 most likely
<> Post-copulus call seperated into 2 distinct parts
+ last part of call becomes longer after successive matings with the same individual
- original thought: mate declaration adaption by lower-ranking female to inform alpha/ rest of troop of successive and progressive consorting relative to peak receptiveness, as a function of pin-pointing paternity to reduce the likelihood of erroneous and costly infanticide [would require co-function with theorized mediation of female interaction by dominant male/s (Palombit et al., 1999.)]
<>With all available evidence, points to directional post-copulatory mate selection, suggests little or no genotypic consideration or sperm competition

2.
<>2-3 individuals, alpha male included, make vocalizations every 2-5 minutes, with alpha often making the last call to terminate the sequence
<>Multiple-source calls possibly a way for lagging troop members, alpha and lookouts to triangulate a moving positional average toward which the troop will move, or around which they congregate and mediate with the direction of the alpha in the face of environmental obstacles or perceived danger.
-[Would appendice the known ability of Chacma Baboons to map out their range topologically in place of using Euclidean geometries (De Raad, A.L., Hill, R.A., 2019)]

3.
<>Subdominant males are found more often on troop periphery [Evidenced in Kamberg Nature Reserve and Golden Gate NP Troops], and stay within earshot of fringe troop members, possibly attempting to occasionally pull low-ranking females away to venture out in search of unexplored food patches (potential troop fision?). Troop itself usually spread out over large areas in mountainous terrain, with broad interspersions between social clusters.

Posted on October 29, 2022 04:36 PM by anthonywalton anthonywalton | 0 comments | Leave a comment

July 10, 2022

Genus Rhynchosia plasticity: A need for further revision

1st observation:
Southern Cape, Western Garden Route area
Habitat - Fringe of thicket; outer margins of short and sparser limestone Fynbos
Growth Habit - Twining creeper
Description - Leaves trichotomously branched from secondary growth meristem; Leaf margins slightly inturned toward adaxial surface, with no hairs, and no lobing; upper leaf surface with pubescent hairs/ tubercles; estipulate

2nd observation:
Muden district, KZN
Habitat - Floor layer of closed canopy afrotemperate scarp forest
Growth Habit - Erect to semi-erect Cryptophyte (Forbe, unbranched at base)
Description - Leaves trichotomously branched from secondary growth meristem; distal margins of leaves broadly lobed with notable tapering towards apex; margins with short hairs throughout especially toward petiolar base; margins completely flush with midvein; upper surface of leaf smooth/ glabrous; estipulate

Posted on July 10, 2022 03:34 PM by anthonywalton anthonywalton | 2 observations | 0 comments | Leave a comment

July 01, 2022

Genus Thestor: 2 species and their Characters

T. protumnus:
Nominate found in Cape Peninsula
Eggs laid near Ants nests, often singularly but some in clusters
Larvae hatches and by 3rd instar, taken by Ants into underground chambers where it is possibly fed by them, and feeds further on live Coccids (Homoptera), enticing them closer and to remain calm with pheromones. Total length at end of 3rd instar is +-6mm
Once larvae is midway into 4th instar, it will enter into pupation and if need be remain in diapause in this state (up to 30 days) until conditions are favourable before chrysalis emerges, or else it will enter a new larval instar. By end of 4th instar, larva is 18mm long
Pupation is on hollow of ants nest just beneath soil or rock

T. basutus spp. basutus:
Found in higher lying areas from Eastern Cape, through Natal and Mpumalanga Drakensberg escarpment and slightly further north
Eggs laid mostly singularly, broader gaps between oviposition
Larvae hatches and feeds on Verbena plants also visited by Ants and Homoptera, but only at the end of 4th instar is it taken by ants into the nest and left unattended to pupate soon after. At end of 3rd instar, measures 7mm in length, and reaches 18mm in an indeterminate amount of time (perhaps responding to environmental cues)
An additional brood may occur in some populations (perhaps as a factor of geographic position)
Pupa formed in Ants nest, where Chrysalis emerges and slowly exits the tunnels

Conclusion:
T. protumnus adapted to edaphic specialization through contigency with highly localized weather events in a smaller geographic space (larvae grow slower than T. basutus but can stay underground longer?) in addition to possible higher flexibility in oviposition spatial selection (switching from singular to clustering). Evidenced in in fresh Chrysalis sightings from September through to early January

T. basutus ssp. basutus adapted to broader scale climatic onsets which are less predictable (front blowing in snow or cold weather to the mountains). Grows faster, possibly pupates faster (?), maybe in response to the requirement of more time 'on-the'wing' to find colonies of larval foodplants segmented in the grassland landscape. Can't spend too long in ants nest but can do 2 broods, if perhaps one should fail to produce a certain threshold of adult recruitment

Source: Life Histories of the South African Lycaenid Butterflies; by G.C Clark and C.G Dickson (Purnell; 1971)

Posted on July 01, 2022 12:02 PM by anthonywalton anthonywalton | 2 observations | 0 comments | Leave a comment

June 15, 2022

Seed predation in Helichrysum oligopappum

H. oligopappum begins flowering in late February/ early March (mid-to-late March peak) in northern populations
Seed dispersal completed by (on average) early to late April. Soon after peak flowering
Residual seed left on broader, angulate inflorescences into autumn and beginning of Winter, but heavily predated on by Pentid beetles (significant crass loads left in hollowed papii)

Posted on June 15, 2022 11:03 AM by anthonywalton anthonywalton | 1 observation | 0 comments | Leave a comment

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