Anja Rösler

A DIVERSE PATCH REEF FROM TURBID HABITATS IN THE MIDDLE MIOCENE (EAST KALIMANTAN, INDONESIA)

ABSTRACT The Kutai Basin (East Kalimantan, Indonesia) contains a rich and well-preserved Miocene fossil record of small patch reefs that developed under the influence of high siliciclastic input associated with the progradation of the Mahakam Delta. In this study, we reconstruct the biodiversity and paleoenvironments on one of these delta-front, mixed carbonate-siliciclastic systems that developed at the Serravallian–Tortonian boundary near the city of Samarinda. In two newly exposed sections, we analyzed the sedimentology and distribution of the main fossil biota including corals, foraminifers, coralline algae, and bryozoans. Seven facies are herein defined, including two dominated by platy corals and two by larger benthic foraminifera. Facies distributions were driven by changes in depth and variations in terrigenous input within a range of delta-front habitats. Despite the turbid conditions, fossil assemblages are highly diverse, including 69 coral species and 28 bryozoan species that occur in coral-dominated facies. Crustose coralline algae were mainly associated with the coral-dominated facies. Larger benthic foraminifera showed broader ecological tolerance within the range represented in the studied sections and thus are common in most facies. These diverse patch reef ecosystems were able to cope with high siliciclastic input during the early development of the Miocene coral reef biota.

House sparrows selectively eject parasitic conspecific eggs and incur very low rejection costs

Most host species of obligate interspecific brood parasites are under strong selection because such parasitism, e.g., that involving evictor nestmates, is highly costly. Egg rejection is one of the most efficient host defences against avian brood parasites. Many hosts have thus evolved egg-recognition ability and rejection behaviour. However, this defensive mechanism has not evolved in most species where only intraspecific brood parasitism occurs, probably because (1) the eggs of conspecific females are very similar in appearance, making egg rejection less likely to emerge, and (2) such parasitism is frequently less costly than interspecific parasitism. Using a captive population of house sparrows (Passer domesticus) with a low breeding density, we here provide new evidence showing that this species actually has a fine capacity to discriminate conspecific eggs and to eject them (44.2% of foreign eggs ejected) while incurring very low rejection costs (4.2% of own eggs ejected). This result contradicts those previously found in high-density house sparrow populations in which very high rejection costs and very high clutch desertion rates were reported, probably as a consequence of intraspecific competition and infanticide provoked by the high breeding density. The house sparrow has only rarely been reported as the host of an interspecific brood parasite, which implies that it is a newly described example of an altricial species in which egg ejection has evolved and is maintained in response to intraspecific brood parasitism.

Phylogenetic relationships of corallinaceae (Corallinales, Rhodophyta): taxonomic implications for reef-building corallines.

A new, more complete, five‐marker (SSU, LSU, psbA, COI, 23S) molecular phylogeny of the family Corallinaceae, order Corallinales, shows a paraphyletic grouping of seven well‐supported monophyletic clades. The taxonomic implications included the amendment of two subfamilies, Neogoniolithoideae and Metagoniolithoideae, and the rejection of Porolithoideae as an independent subfamily. Metagoniolithoideae contained Harveylithon gen. nov., with H. rupestre comb. nov. as the generitype, and H. canariense stat. nov., H. munitum comb. nov., and H. samoënse comb. nov. Spongites and Pneophyllum belonged to separate clades. The subfamily Neogoniolithoideae included the generitype of Spongites, S. fruticulosus, for which an epitype was designated. Pneophyllum requires reassesment. The generitype of Hydrolithon, H. reinboldii, was a younger heterotypic synonym of H. boergesenii. The evolutionary novelty of the subfamilies Hydrolithoideae, Metagoniolithoideae, and Lithophylloideae was the development of tetra/bisporangial conceptacle roofs by filaments surrounding and interspersed among the sporangial initials.

CORALLINE ALGAE FROM THE MIOCENE MAHAKAM DELTA (EAST KALIMANTAN, SOUTHEAST ASIA)

ABSTRACT Miocene crustose coralline algae (CCA) from Southeast Asia are poorly known, although the Miocene is the epoch of the onset of the biodiversity hotspot in the region and CCA are crucial to understanding the evolutionary history of reef building. To fill this knowledge gap, CCA from early and middle Miocene reefs and related carbonates in the Kutai Basin in East Kalimantan (Borneo, Indonesia) have been studied. The Kutai Basin was dominated by siliciclastic sediments of the proto-Mahakam Delta. Locally, carbonate buildups occur lateral to, or within, the deltaic succession. CCA in the Kutai Basin occur in carbonate beds that were deposited in a low-energy shallow-water platform setting and in association with coral reefs, encrusting the corals or bioclasts. Two main CCA assemblages are recognized herein: (1) a shallow-water assemblage (S-assemblage), dominated by Neogoniolithon spp., thick crusts of Spongites spp., and Hydrolithon spp.; and (2) the D-assemblage, which consists mainly of thin crusts of Lithothamnion spp., Mesophyllum spp., and Sporolithon spp., and is interpreted to have developed in darker waters. Light reduction in reefs in the proto-Mahakam Delta is interpreted to reflect either increased water depth or higher turbidity resulting from higher siliciclastic input. Assemblages with intermediate composition (I-assemblages) also occur. Common CCA with large cell fusions and groups of heterocysts, typical features of modern reef CCA, in the S-assemblages in the middle Miocene of East Kalimantan reflect the initiation of the reef-building CCA flora in the Indo-Pacific region. The occurrence of this kind of CCA confirms the biogeographic differentiation of a tropical reef flora.

Timing of the evolutionary history of Corallinaceae (Corallinales, Rhodophyta)

The temporal dimension of the most recent Corallinaceae (order Corallinales) phylogeny was presented here, based on first occurrence time estimates from the fossil record. Calibration of the molecular clock of the genetic marker SSU entailed a separation of Corallinales from Hapalidiales in the Albian (Early Cretaceous ~105 mya). Neither the calibration nor the fossil record resolved the succession of appearance of the first three emerging subfamilies: Mastophoroideae, Corallinoideae, and Neogoniolithoideae. The development of the tetra/bisporangial conceptacle roofs by filaments surrounding and interspersed among the sporangial initials was an evolutionary novelty emerging at the Cretaceous–Paleogene boundary (~66 mya). This novelty was shared by the subfamilies Hydrolithoideae, Metagoniolithoideae, and Lithophylloideae, which diverged in the early Paleogene. Subclades within the Metagoniolithoideae and Lithophylloideae diversified in the late Oligocene–middle Miocene (~28–12 mya). The most common reef corallinaceans (Hydrolithon, Porolithon, Harveylithon, “Pneophyllum” conicum, and subclades within Lithophylloideae) appeared in this interval in the Indo‐Australian Archipelago.

Context-dependent effects of an experimental increase of hunger level in house sparrow nestlings

Exploring the links between parental supply and nestling demands and between nestling demand and food supply is of central importance for understanding the evolution of parent-offspring communication. It has been suggested that optimal food supply by parents and begging effort of nestlings are context dependent, and we here test some predictions of this hypothesis. House sparrow (Passer domesticus) nestlings were experimentally fed with a pharmacological appetitive stimulant (cyproheptadine) that increases nestling demands, and explore its effect on nestling growth (i.e. body mass and tarsus length), which can be considered as the net payoff of inflated and costly offspring demand. As assumed by the experimental protocol, nestlings with an exaggerated demand were preferentially fed by parents. In accordance with the hypothesis, net benefits in terms of growth were mainly detected in first breeding attempt of parents that successfully reared three broods. Because costs associated with parental feeding should be lower for first breeding attempts and for parents of higher phenotypic quality (those able to successfully rear three clutches), our results provide to our knowledge, the first experimental evidence supporting a dynamic role of costs of food supply affecting net payoff of offspring demands, which may help to understand the mechanisms allowing the evolutionary equilibrium between intensities of offspring begging and parental provisioning.Significance statementBoth feeding and begging for food are costly activities for offspring and parents respectively. Rewards of such behaviours in terms of food receiving and reproductive success should vary depending on ecological conditions (i.e. food availability for offspring and physical condition of parents). Here we pharmacologically exaggerated appetitive of house sparrows (Passer domesticus) nestlings and explore its effect on parental behaviour and on nestling growth (i.e. body mass and tarsus length). The expected benefits were mainly detected for first breeding attempts and only in nests of adults that were able to rear two more broods, that is, when costs of feeding the offspring by adults are lower. Our results provide to our knowledge, the first experimental evidence supporting dynamic outcomes of offspring demands and parental provisioning, which is essential for understanding the evolution of parent-offspring communication.

Adeylithon bosencei gen. et sp. nov. (Corallinales, Rhodophyta): a new reef-building genus with anatomical affinities with the fossil Aethesolithon

Adeylithon gen. nov. with one species, A. bosencei sp. nov., belonging to the subfamily Hydrolithoideae is described from Pacific coral reefs based on psbA sequences and morpho‐anatomy. In contrast with Hydrolithon, A. bosencei showed layers of large polygonal “cells,” which resulted from extensive lateral fusions of perithallial cells, interspersed among layers of vegetative cells. This anatomical feature is shared with the fossil Aethesolithon, but lacking DNA sequences from the fossils and the fragmentary nature of Aethesolithon type material, we cannot ascertain if Adeylithon and Aethesolithon are congeneric. Morpho‐anatomical features of A. bosencei were generally congruent with diagnostic features of the subfamily Hydrolithoideae: (i) outline of cell filaments entirely lost in large portions due to pervasive and extensive cell fusions, (ii) trichocytes not arranged in tightly packed horizontal fields, (iii) basal layer without palisade cells, and (iv) cells lining the canal pore oriented more or less perpendicular to roof surface and not protruding into the canal. However, it showed a predominant monomerous thallus organization and trichocytes were disposed in large pustulate, horizontal fields, although they were not tightly packed and did not become distinctly buried in the thallus. Only mature tetrasporangial conceptacles were observed, therefore the type of conceptacle roof formation remained undetermined. Adeylithon bosencei occurs on shallow coral reefs, in Australia, Papua New Guinea, and South Pacific islands (Fiji, Vanuatu). Fossil Aethesolithon is considered an important component of shallow coral reefs since the Miocene; fossil records showed a broad Indo‐Pacific distribution, but a long‐term process of range contraction in the last 2.6 million years, resulting in an overlap with the distribution of the extant Adeylithon. While the congeneric nature of extant and fossil taxa remained uncertain, similarities in morpho‐anatomy, habitat, and distribution may indicate that both taxa likely shared a common ancestor.