Alasemenia: The Earliest Three-Winged Ovule Without a Cupule

Core Concepts

The Famennian ovule Alasemenia tria represents the earliest known ovule with three broad, wing-like integumentary lobes that extend outwards, lacking a protective cupule. This suggests the integuments of the earliest ovules evolved functions in wind dispersal and probable photosynthetic nutrition.

Abstract

The paper describes a new taxon of Famennian ovules, Alasemenia tria gen. et sp. nov., from the Late Devonian of China. Key findings: Alasemenia ovules are terminally borne on dichotomous branches and lack a cupule. Each ovule possesses three broad, wing-like integumentary lobes that radially extend outwards, fold inwards along the abaxial side, and enclose most of the nucellus. The free parts of the integumentary lobes account for 32-45% of the ovule length, suggesting a role in wind dispersal. Transverse sections reveal the three lobes are symmetrically arranged, with one lobe sometimes compressed along the bedding plane. Mathematical analysis indicates three-winged seeds like Alasemenia are more efficient for wind dispersal compared to one, two, or four-winged seeds. The authors suggest the integumentary wings of Alasemenia, as well as other Famennian ovules like Guazia, represent an early evolution of wind dispersal mechanisms in seed plants, preceding the appearance of other dispersal adaptations like plumes and pappus.

Stats

The ovules are 25.0-33.0 mm long and 3.5-5.6 mm at the maximum width (excluding the width of outward extension of integumentary wings). The integumentary lobes are 1.2-2.3 mm at the maximum width and free for 8.3-14.8 mm distance (32%-45% of the ovule length). The nucellus is ca. 10-11.7 mm long and 1.2-1.7 mm at the maximum width.

Quotes

"Alasemenia suggests that the integuments of the earliest ovules without a cupule evolved functions in wind dispersal and probable photosynthetic nutrition." "Current evidence indicates that seeds with three or four wings occurred first in the Late Devonian. They were followed by two- or three-winged seeds in the Carboniferous, and then by single-winged seeds in the Permian." "The mathematical analysis of winged seeds indicates that the relative efficiency of three-winged seeds is obviously better than that of single- and two-winged seeds, and is close to that of four-winged seeds."

Key Insights Distilled From

Alasemenia, the earliest ovule with three wings and without cupule

by Wang,D., Yan... at www.biorxiv.org 10-14-2023

https://www.biorxiv.org/content/10.1101/2023.10.11.561822v1

Deeper Inquiries

How did the evolution of integumentary wings in Famennian ovules like Alasemenia influence the subsequent diversification of seed dispersal mechanisms in later seed plant lineages?

The evolution of integumentary wings in Famennian ovules, such as Alasemenia, played a crucial role in shaping the subsequent diversification of seed dispersal mechanisms in later seed plant lineages. These early integumentary wings provided a novel mechanism for wind dispersal, allowing seeds to be carried over longer distances by the wind. This adaptation likely increased the efficiency of seed dispersal, enabling plants to colonize new habitats and expand their range. The presence of integumentary wings in Famennian ovules like Alasemenia paved the way for the development of more sophisticated dispersal mechanisms in later seed plant lineages. The success of wind dispersal as a strategy likely led to the evolution of additional adaptations for seed dispersal, such as plumes, pappi, and parachutes in later plant lineages. The early evolution of integumentary wings in Famennian ovules set the stage for the diversification of seed dispersal mechanisms and contributed to the success and spread of seed plants in various environments.

What other morphological or anatomical adaptations might have accompanied the evolution of integumentary wings in early seed plants?

Alongside the evolution of integumentary wings in early seed plants like Alasemenia, several other morphological and anatomical adaptations may have accompanied this evolutionary development. These adaptations would have worked synergistically to enhance the efficiency of seed dispersal and reproductive success in early seed plants. Reduction in size and weight: The evolution of integumentary wings may have been accompanied by a reduction in the size and weight of seeds. Lighter seeds are more easily carried by the wind, increasing the distance they can travel for dispersal. Changes in seed shape: The shape of seeds may have been modified to optimize aerodynamics and enhance wind dispersal. Streamlined seed shapes would reduce air resistance and improve the efficiency of seed dispersal. Development of specialized structures: Alongside integumentary wings, early seed plants may have developed specialized structures to aid in seed dispersal. These could include structures for attachment to animals or mechanisms for water dispersal. Enhanced seed protection: With the evolution of integumentary wings, there may have been adaptations to enhance seed protection. This could involve the development of tougher seed coats or structures to prevent desiccation during dispersal. Changes in seed germination: The evolution of integumentary wings may have been accompanied by changes in seed germination strategies. Seeds with integumentary wings may have evolved mechanisms to ensure successful germination upon reaching suitable habitats.

What insights can the study of Alasemenia and other Famennian ovules provide about the early reproductive biology and ecology of the earliest seed plants?

The study of Alasemenia and other Famennian ovules offers valuable insights into the early reproductive biology and ecology of the earliest seed plants. These insights shed light on the evolutionary history of seed plants and the adaptations that allowed them to thrive in ancient ecosystems. Reproductive strategies: The presence of integumentary wings in Famennian ovules like Alasemenia suggests that early seed plants had already developed sophisticated reproductive strategies, including mechanisms for seed dispersal. This indicates a high level of reproductive complexity and adaptation in early seed plants. Ecological interactions: The study of Famennian ovules provides information about the ecological interactions of early seed plants. The presence of wind-dispersed seeds suggests that these plants were interacting with their environment and utilizing wind as a dispersal agent to colonize new areas. Evolutionary milestones: The presence of integumentary wings in Famennian ovules represents an important evolutionary milestone in the history of seed plants. It marks the early development of adaptations for seed dispersal, which played a crucial role in the success and diversification of seed plants over time. Adaptive radiation: The study of Alasemenia and other Famennian ovules contributes to our understanding of the adaptive radiation of early seed plants. It highlights the diverse strategies that plants employed to reproduce and disperse their seeds, leading to the colonization of different habitats and the expansion of plant diversity. Paleoecological implications: By studying Famennian ovules, researchers can reconstruct ancient ecosystems and understand the role of early seed plants in shaping these environments. Insights into the reproductive biology and ecology of the earliest seed plants provide valuable information for understanding the dynamics of ancient plant communities.