Howard Lasker

University at Buffalo, State University of New York | SUNY Buffalo · Department of Geology

Octocorals have increased in abundance on many Caribbean coral reefs, and at some sites "octocoral forest" may be a better community descriptor than "coral reef." Implicit to the concept of a forest is that structural elements, trees, colonies, etc., alter the environment in ways that affect the structural elements themselves and the organisms that...

In the Caribbean, reef-building scleractinian corals have declined precipitously and octocorals have emerged as one of their main successors. The success of octocorals and the formation of octocoral forests has been attributed to their continuing recruitment to reef habitats, as well as tolerance to pollution, reduced direct competition with sclera...

The reproductive biology of the branching octocoral Antillogorgia americana was studied at a site on the Caribbean coast of Panama in 1990–1991 by examining the reproductive status of 11 colonies across 14 months. Colonies were gonochoric. The presence of large and mature eggs or spermaries was allochronic across colonies and months, with peak gona...

As the major form of coral reef regime shift, stony coral to macroalgal transitions have received considerable attention. In the Caribbean, however, regime shifts in which scleractinian corals are replaced by octocoral assemblages hold potential for maintaining reef associated communities. Accordingly, forecasting the resilience of octocoral assemb...

Unlike reef-building, scleractinian corals, Caribbean soft corals (octocorals) have not suffered marked declines in abundance associated with anthropogenic ocean warming. Both octocorals and reef-building scleractinians depend on a nutritional symbiosis with single-celled algae living within their tissues. In both groups, increased ocean temperatur...

The three‐dimensional structure of habitats is a critical component of species' niches driving coexistence in species‐rich ecosystems. However, its influence on structuring and partitioning recruitment niches has not been widely addressed. We developed a new method to combine species distribution modelling and structure from motion, and characteriz...

Background Among species with size structured demography, population structure is determined by size specific survival and growth rates. This interplay is particularly important among recently settled colonial invertebrates for which survival is low and growth is the only way of escaping the high mortality that small colonies are subject to. Gorgon...

The 3-dimensional structure of habitats is a critical component of species' niches driving coexistence in species-rich ecosystems. However, its influence on structuring and partitioning recruitment niches has not been widely addressed. We developed a new method to combine Species Distribution Modeling and Structure from Motion and characterized thr...

The 3-dimensional structure of habitats is a critical component of species’ niches driving coexistence in species-rich ecosystems. However, its influence on structuring and partitioning recruitment niches has not been widely addressed. We developed a new method to combine Species Distribution Modeling and Structure from Motion and characterized thr...

Despite the importance of historical data in quantifying shifting conditions, information legacies are being lost through oversight and retirement of researchers. We highlight the recovery of two long-term research sites in Caribbean octocoral forests and call for preservation of other legacy sites and associated data before these locations become...

Caribbean octocorals have not suffered the decades long decline in abundance that has plagued reef-building scleractinian corals. Their success and the formation of octocoral forests has been attributed to their continuing recruitment to reef habitats. Assessing the processes controlling recruitment is essential to the understanding the success of...

ecological and evolutionary consequences. In lotic freshwater systems, landscape features such as barriers or connectors, can affect dispersal and thus gene flow. It is of special interest to characterize population genetic structure in the presence of impassable barriers because they can restrict dispersal and thus isolate populations. On the othe...

Octocorals are conspicuous members of coral reefs and deep-sea ecosystems. Yet, species boundaries and taxonomic relationships within this group remain poorly understood, hindering our understanding of this essential component of the marine fauna. We used a multifaceted approach to revisit the systematics of the Caribbean octocorals Plexaura homoma...

Declines in abundance of scleractinian corals on shallow Caribbean reefs have left many reefs dominated by forests of arborescent octocorals. The ecological mechanisms favoring their persistence require exploration. We quantified octocoral communities from 2014 to 2019 at two sites in St. John, US Virgin Islands, and evaluated their dynamics to ass...

Little is known about how the reef matrix on which corals attach influences the distribution patterns of recruits of sympatric sessile taxa within coral reef communities. This matrix, shaped by biotic and abiotic reef structures, creates fine-scale microhabitats (mm- cm scale) that may be relevant to coral settlement and survival, in turn, the asse...

Quantification of the invasion of Ophiothela mirabilis across reefs in St. John, USVI

Recruitment is a key demographic process for maintenance of local populations and recovery following disturbance. For marine invertebrates, distribution and abundances of recruits are impacted by spatiotemporal variation in larval supply, settlement rates and post-settlement survival. However, for colonial and modular organisms, differences in surv...

Algal cover has increased and scleractinian coral cover has steadily declined over the past 40 years on Caribbean coral reefs, while octocoral abundance has increased at sites where abundances have been monitored. The effects of algal cover on recruitment may be a key component in these patterns, as upright octocoral recruits may escape competition...

Correct species identification and delineation are crucial for effective conservation and management. However, species delineation can be problematic in the presence of morphological ambiguities due to phenotypic plasticity, convergence, and/or interspecific hybridization. Here, we investigated the degree of hybridization between two closely related...

Recent shifts in the presence and abundance of species on shallow Caribbean coral reefs have left octocorals as the dominant functional group on some reefs, creating an ‘animal forest’ with an associated canopy. This transition changes the reef profile potentially affecting flow and sedimentation. We examined the effects of an octocoral forest on t...

Patterns of population biology and community structure can be studied by looking closely at the ontogeny and reproductive biology of reef-building organisms. This knowledge is particularly important for Caribbean octocorals, which seem to be more resilient to long-term environmental change than scleractinian corals and provide some of the same ecol...

Successful recruitment is critical to the maintenance and resilience of populations and may be at the core of the transition from scleractinian- to octocoral-dominated faunas on some Caribbean reefs. For sessile invertebrates, recruitment incorporates the composite effects of larval supply, settlement and survival. The relative success of these pro...

Coral reefs throughout the tropics have experienced large declines in the abundance of scleractinian corals over the last few decades, and some reefs are becoming functionally dominated by animal taxa other than scleractinians. This phenomenon is striking on many shallow reefs in the tropical western Atlantic, where arborescent octocorals now are n...

Algal cover has increased and scleractinian coral cover has steadily declined over the past 40 years on Caribbean coral reefs. In contrast, octocoral abundance has increased at those sites where octocoral abundances have been monitored. The effects of algal cover on recruitment may be a key component in these patterns, as upright octocoral recruits...

Understanding the ontogeny and reproductive biology of reef-building organisms can shed light on patterns of population biology and community structure. This knowledge is particularly important for Caribbean octocorals, which seem to be more resilient to long-term environmental change than scleractinian corals and provide some of the same ecologica...

After centuries of human-mediated disturbances, Caribbean reef communities are vastly different from those described in the 1950s. Many are functionally dominated by macroalgae, but this community state represents only one of several possibilities into which present-day coral reefs can transition. Octocorals have always been abundant on Caribbean r...

Lampsilis bracteata (Gould), the Texas Fatmucket, is a regional endemic species in the central Texas biogeographic province which is a candidate to be listed as threatened or endangered under the Endangered Species Act of 1973. Lampsilis bracteata is morphologically similar to the common species L. hydiana (Lea). Here, we examine the molecular taxo...

The coral reef crisis is defined by declining cover of scleractinians, but on Caribbean reefs it also is associated with increasing abundances of octocorals. The demographic causes of these increases are not understood, but parallels between marine ‘forests’ of octocorals, and terrestrial forests of trees (e.g. formation of a 3-dimensional framewor...

DNA barcoding is a useful tool for documenting the diversity of metazoans. The most commonly used barcode markers, 16S and COI, are not considered suitable for species identification within some "basal" phyla of metazoans. Nevertheless metabarcoding studies of bulk mixed samples commonly use these markers and may obtain sequences for "basal" phyla....

Octocorals have increased in abundance on a number of Caribbean reefs, but this trend has largely been reported with functional group or genus resolution. A species-level analysis of octocoral communities in St. John, US Virgin Islands was conducted to better understand how this taxon will respond to changing conditions based on their synecology at...

Biological traits of marine benthic species have important effects on the extent of lar- val dispersal. Yet, empirical characterizations of many of these traits, which are critical data for parameterizing models of larval dispersal, remain scant for most species, particularly corals. We characterized spawning, larval development, settlement dynamic...

We evaluated whether long-Term change on fringing reefs (7-9 m depth) around St. John, U Virgin Islands, conformed to the 'coral reef crisis' involvin ongoing collapse of community structure. Annua photoquadrats at 6 sites were used to measur octocoral abundance (by genus) and the cover of scleractinian (by species), macroalgae, crustose corallin a...

Concern about the future of coral reef communities, and the recognition that larval dispersal plays a key role in the resilience of populations has spurred research to determine whether populations are connected by larval exchange or instead maintained by local supply of larvae. In the process of these endeavors, the generalized belief that marine...

The incidence of octocoral-octocoral interactions and the physical effects of the interactions were determined in surveys of 29 branching octocoral species at 2 sites in St. John, U.S. Virgin Islands. Close proximity, defined as the bases or branches of octocorals being within 5 cm of each other, creates the potential for direct competitive interac...

While the decline in cover of scleractinian corals on Caribbean reefs is well known, little attention has been paid to other taxa that might covary in abundance. This study focused on octocorals around St. John and St. Thomas, US Virgin Islands, in order to: (1) describe variation in octocoral communities, (2) test for similarity in distribution of...

Patterns of dispersal and connectivity of the Caribbean gorgonian Antillogorgia elisabethae in The Bahamas were assessed in both adults and recently settled recruits from 13 sites using microsatellite loci. Adult populations along the Little Bahama Bank (LBB) exhibited a clear pattern of isolation by distance (IBD) which described 86% of the varian...

The decline in abundance of scleractinian corals over the past three decades in the Caribbean has raised the possibility that other important benthic taxa, such as octocorals, are also changing in abundance. We used photoquadrats taken over 20 yr from reefs (7–9 m depth) at six sites on the south coast of St. John, US Virgin Islands, to test the hy...

Species level identification of octocorals is often based on the form of skeletal elements, the sclerites. Morphological variation in sclerites across and within habitats complicates both species delineation and the identification of specimens, both of which are essential for characterizing and understanding octocoral diversity. In order to quantif...

The reproductive biology of the Caribbean gorgonian Antillogorgia hystrix was studied in the shallow-water reefs of Cross Harbour, Great Abaco (The Bahamas) from 2009 to 2010. Antillogorgia hystrix is an internal brooder that reproduces annually. The population at Cross Harbour was gonochoric and the sex ratio was skewed toward females (~3:1). Ooge...

Larval dispersal is a critical component of marine species’ life histories because it controls their population dynamics. Dispersal distance can be inferred by the presence and scale of spatial genetic structure (SGS). The larvae of Antillogorgia elisabethae, a surface brooding Caribbean octocoral, have been observed to settle within meters of mate...

We report 7 new polymorphic microsatellite loci of the Caribbean gorgonian Antillogorgia elisabethae, and assess their utility as highly polymorphic markers for population genetic studies. We also found an indel of 4 base pairs in one of the microsatellite flanking region that can be used as an independent locus. A. elisabethae is of special intere...

Disturbance events are an important component of the ecology of coral reefs and increasingly frequent disturbances coupled with a lack of population resilience may contribute to changes in the structure of coral reef communities. The harvest of the Caribbean octocoral Antillogorgia elisabethae provides an opportunity to explore the relationship bet...

Recruits of the Caribbean scleractinian coral Porites astreoides and the octocoral Briareum asbestinum were established on artificial substrata and reared on a reef in cages designed to exclude various classes of organisms known to feed on corals. Post-settlement survivorship of recruits was measured for periods of 2 weeks (B. asbestinum) and 1 mon...

In benthic communities sponges commonly outcompete other organisms in the race for suitable space. Superior competitive ability allows them to grow and overgrow other sessile organisms, some of these being octocorals. Acquiring substratum space, a resource often more limiting than food, is the obvious benefit of these competitive interactions. Howe...

Clonal organisms have complex life histories in which traits such as reproductive maturity and fecundity are affected by colony size. Thus changes in reproduction due to tissue loss have the potential to affect population dynamics even among seemingly healthy populations. At sites in The Bahamas the octocoral Pseudopterogorgia elisabethae, which pr...

For octocorals, sexual reproductive processes are fundamental to maintaining populations and influencing macroevolutionary processes. While ecological data on octocorals have lagged behind their scleractinian counterparts, the proliferation of reproductive studies in recent years now enables comparisons between these important anthozoan taxa. Here...

Species descriptions of most alcyonacean octocorals rely heavily on the morphology of sclerites, the calcium carbonate spicules embedded in the soft tissue. Sclerites provide taxonomic characters for species delineation but require qualitative descriptions, which introduce ambiguities in recognizing morphological features. Elliptical Fourier analys...

Species descriptions of most alcyonacean octocorals rely heavily on the morphology of sclerites, the calcium carbonate spicules embedded in the soft tissue. Sclerites provide taxonomic characters for species delineation but require qualitative descriptions, which introduce ambiguities in recognizing morphological features. Elliptical Fourier analys...

The combination of coloniality and symbiosis in Scleractinia is thought to confer competitive advantage over other benthic invertebrates, and it is likely the key factor for the dominance of corals in tropical reefs. However, the extant Scleractinia are evenly split between zooxanthellate and azooxanthellate species. Most azooxanthellate species ar...

Coral reef species are frequently the focus of bio-prospecting, and when promising bioactive compounds are identified there is often a need for the development of responsible harvesting based on relatively limited data. The Caribbean gorgonian Pseudopterogorgia elisabethae has been harvested in the Bahamas for over a decade. Data on population age...

Coral reef anthozoans exhibit extensive morphological variation across and within environmental clines making it difficult to define species boundaries. The relative contributions of genetic variation and ecophenotypic plasticity to the observed phenotypic variation are unknown in most cases. The branching octocoral Pseudopterogorgia elisabethae is...

Many sessile organisms rely on the transport of one or both types of gametes for reproductive success. While sperm limitation has been reported in some species, high fertilization success has been observed in others including the branching octocoral Pseudopterogorgia elisabethae. In such cases, males may compete for eggs to fertilize and the local...

Octocorals are commonly identified from the structure of their calcium carbonate sclerites. However, small recruits cannot always be identified in this manner. Primers for microsatellite loci developed for the Caribbean branching octocoral Pseudopterogorgia elisabethae were used to identify six common Pseudopterogorgia spp. on the Little Bahama Ban...

The modular construction of colonial organisms can generate complex growth patterns that incorporate both growth and partial mortality. These patterns often confound simple age based descriptions of growth but, in some cases, modularity can generate predictable patterns of colony growth that are amenable to modeling approaches more commonly used in...

Colonies of the Caribbean gorgonian Pseudopterogorgia elisabethae release eggs that are retained on the colony surface where they are fertilized and then develop. In December 2001, spawning on San Salvador Island, Bahamas, occurred over 6 d, with spawning by any one colony limited to 1-3 d. With the exception of the first and last days of the spawn...

Colonies of the branching Caribbean gorgonian Pseudopterogorgia elisabethae were subjected to partial mortality at 2 sites in the Bahamas to study how colony growth responds to disturbances such as harvesting, grazing, and storm damage. Colonies were clipped so that either 4 branches or 10 branches remained. Growth rates of branches were then monit...

Octocorals, like many other colonial benthic invertebrates, exhibit remarkable levels of morphological variability. The basis for this variability has been largely unexplored. Plexaura flexuosa Lamouroux, a common Caribbean octocoral, is found in virtually all reef habitats, and exhibits habitat-related differences in growth rates and fecundity. Po...

The primary mechanism of gene flow in marine sessile invertebrates is larval dispersal. In Pseudopterogorgia elisabethae, a commercially important Caribbean gorgonian coral, a proportion of the larvae drop to the substratum within close proximity to the maternal colony, and most matings occur between individuals in close proximity to each other. Su...

The reproductive biology, development, and planula behavior of the gorgonian Pseudopterogorgia elisabethae were studied at 2 sites in the Bahamas between 1996 and 2001. Colonies were gonochoric, and females brooded planulae on the colony surface. Gonads were observed only in colonies 18 cm high or larger. Spawning was asynchronous within and betwee...

One of the advantages of modular colonial growth is the capability to recover after partial mortality. Tolerance to partial mortality is a known property of some resistant species of plants that respond to mortality with vigorous regrowth or overcompensation. It is not clear whether modular marine invertebrates such as octocorals overcompensate. Th...

Despite the universality of branching patterns in marine modular colonial organisms, there is neither a clear explanation about the growth of their branching forms nor an understanding of how these organisms conserve their shape during development. This study develops a model of branching and colony growth using parameters and variables related to...

We report on the isolation and characterization of five polymorphic microsatellites in the gorgonian Pseudopterogorgia elisabethae from genomic DNA-enriched libraries. Forty-four microsatellites were screened from the libraries with the oligonucleotide probe (CA)12. Five of the screened microsatellites were polymorphic. The levels of polymorphism f...

Growth rates of branches of colonies of the gorgonian Pseudopterogorgia elisabethae were monitored for 2 years on a reef at San Salvador Island, Bahamas. Images of 261 colonies were made at 6-month intervals and colony and branch growth analyzed. Branch growth rates differed between colonies and between the time intervals in which the measurements...

Gorgonian octocorals lack corroborated hypotheses of phylogeny. This study reconstructs genealogical relationships among some octocoral species based on published DNA sequences from the large ribosomal subunit of the mitochondrial RNA (lsu-rRNA, 16S: 524bp and 21 species) and the small subunit of the nuclear RNA (ssu-rRNA, 18S: 1815bp and 13 spp) u...

Despite the relative simplicity of their modular growth, marine invertebrates such as arborescent gorgonian octocorals (Octocorallia: Cnidaria) generate complex colonial forms. Colony form in these taxa is a consequence of modular (polyp) replication, and if there is a tight integration among modular and supramodular traits (e.g. polyp aperture, in...

Little is known concerning the fine-scale diversity, population structure, and biogeography for Symbiodinium spp. populations inhabiting particular invertebrate species, including the gorgonian corals, which are prevalent members of reef communities in the Gulf of Mexico, the Caribbean, and the western Atlantic. This study examined the Symbiodinium...